10 Easy Arithmetic Tricks

Math tricks can be terrifying for many people. This list will hopefully improve your general knowledge of mathematical tricks and your speed when you need to do math in your head.




1. The 11 Times Trick

We all know the trick when multiplying by ten - add 0 to the end of the number, but did you know there is an equally easy trick for multiplying a two digit number by 11? This is it:

Take the original number and imagine a space between the two digits (in this example we will use 52:

5_2

Now add the two numbers together and put them in the middle:

5_(5+2)_2

That is it - you have the answer: 572.

If the numbers in the middle add up to a 2 digit number, just insert the second number and add 1 to the first:

9_(9+9)_9

(9+1)_8_9

10_8_9

1089 - It works every time.

2. Quick Square

If you need to square a 2 digit number ending in 5, you can do so very easily with this trick. Mulitply the first digit by itself + 1, and put 25 on the end. That is all!

252 = (2x(2+1)) & 25

2 x 3 = 6

625

3. Multiply by 5

Most people memorize the 5 times tables very easily, but when you get in to larger numbers it gets more complex - or does it? This trick is super easy.

Take any number, then divide it by 2 (in other words, halve the number). If the result is whole, add a 0 at the end. If it is not, ignore the remainder and add a 5 at the end. It works everytime:

2682 x 5 = (2682 / 2) & 5 or 0

2682 / 2 = 1341 (whole number so add 0)

13410

Let’s try another:

5887 x 5

2943.5 (fractional number (ignore remainder, add 5)

29435

4. Multiply by 9

This one is simple - to multiple any number between 1 and 9 by 9 hold both hands in front of your face - drop the finger that corresponds to the number you are multiplying (for example 9×3 - drop your third finger) - count the fingers before the dropped finger (in the case of 9×3 it is 2) then count the numbers after (in this case 7) - the answer is 27.

5. Multiply by 4

This is a very simple trick which may appear obvious to some, but to others it is not. The trick is to simply multiply by two, then multiply by two again:

58 x 4 = (58 x 2) + (58 x 2) = (116) + (116) = 232

6. Calculate a Tip

If you need to leave a 15% tip, here is the easy way to do it. Work out 10% (divide the number by 10) - then add that number to half its value and you have your answer:

15% of $25 = (10% of 25) + ((10% of 25) / 2)

$2.50 + $1.25 = $3.75

7. Tough Multiplication

If you have a large number to multiply and one of the numbers is even, you can easily subdivide to get to the answer:

32 x 125, is the same as:
16 x 250 is the same as:
8 x 500 is the same as:
4 x 1000 = 4,000

8. Dividing by 5

Dividing a large number by five is actually very simple. All you do is multiply by 2 and move the decimal point:

195 / 5

Step1: 195 * 2 = 390
Step2: Move the decimal: 39.0 or just 39

2978 / 5

step 1: 2978 * 2 = 5956
Step2: 595.6

9. Subtracting from 1,000

To subtract a large number from 1,000 you can use this basic rule: subtract all but the last number from 9, then subtract the last number from 10:

1000
-648

step1: subtract 6 from 9 = 3
step2: subtract 4 from 9 = 5
step3: subtract 8 from 10 = 2

answer: 352

10. Assorted Multiplication Rules

Multiply by 5: Multiply by 10 and divide by 2.
Multiply by 6: Sometimes multiplying by 3 and then 2 is easy.
Multiply by 9: Multiply by 10 and subtract the original number.
Multiply by 12: Multiply by 10 and add twice the original number.
Multiply by 13: Multiply by 3 and add 10 times original number.
Multiply by 14: Multiply by 7 and then multiply by 2
Multiply by 15: Multiply by 10 and add 5 times the original number, as above.
Multiply by 16: You can double four times, if you want to. Or you can multiply by 8 and then by 2.
Multiply by 17: Multiply by 7 and add 10 times original number.
Multiply by 18: Multiply by 20 and subtract twice the original number (which is obvious from the first step).
Multiply by 19: Multiply by 20 and subtract the original number.
Multiply by 24: Multiply by 8 and then multiply by 3.
Multiply by 27: Multiply by 30 and subtract 3 times the original number (which is obvious from the first step).
Multiply by 45: Multiply by 50 and subtract 5 times the original number (which is obvious from the first step).
Multiply by 90: Multiply by 9 (as above) and put a zero on the right.
Multiply by 98: Multiply by 100 and subtract twice the original number.
Multiply by 99: Multiply by 100 and subtract the original number.

Bonus: Percentages

Yanni in comment 23 gave an excellent tip for working out percentages, so I have taken the liberty of duplicating it here:

Find 7 % of 300. Sound Difficult?

Percents: First of all you need to understand the word “Percent.” The first part is PER , as in 10 tricks per listverse page. PER = FOR EACH. The second part of the word is CENT, as in 100. Like Century = 100 years. 100 CENTS in 1 dollar… etc. Ok… so PERCENT = For Each 100.

So, it follows that 7 PERCENT of 100, is 7. (7 for each hundred, of only 1 hundred).
8 % of 100 = 8. 35.73% of 100 = 35.73
But how is that useful??

Back to the 7% of 300 question. 7% of the first hundred is 7. 7% of 2nd hundred is also 7, and yep, 7% of the 3rd hundred is also 7. So 7+7+7 = 21.

If 8 % of 100 is 8, it follows that 8% of 50 is half of 8 , or 4.

Break down every number that’s asked into questions of 100, if the number is less then 100, then move the decimal point accordingly.

EXAMPLES:
8%200 = ? 8 + 8 = 16.
8%250 = ? 8 + 8 + 4 = 20.
8%25 = 2.0 (Moving the decimal back).
15%300 = 15+15+15 =45.
15%350 = 15+15+15+7.5 = 52.5

Also it’s usefull to know that you can always flip percents, like 3% of 100 is the same as 100% of 3.

35% of 8 is the same as 8% of 35.

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Crazy Laws From Around the World

We have all heard of some pretty silly laws. Here are twenty-five of the craziest I have ever heard of. (With the exception of #25, I think it is an unwritten law everywhere...)

In Bozeman, Montana, a law prohibits all sexual activity from the front yard of a home after sundown.

In Salt Lake County, Utah, it's illegal to walk down the street carrying a violin in a paper bag.

In San Francisco, it's illegal to pile horse manure more than six feet high on a street corner.

In Devon, Texas, it is against the law to make furniture while you are nude.

In Oklahoma, you can be arrested for making ugly faces at a dog. ( What if it's an ugly dog...?)

In California it is illegal for a vehicle without a driver to exceed 60 miles per hour.

In Florida men seen publicly in any kind of strapless gown can be fined.

In South Carolina it is legal to beat your wife on the court house steps on Sundays.

In Tennessee, you are breaking the law if you drive while sleeping...

In New York, the penalty for jumping off a building is: Death. ( Go figure...)

In Danville, Pennsylvania, all fire hydrants must be checked one hour before all fires.

In Pennsylvania, it's against the law to tie a dollar bill on a string on the ground and pull it away when someone tries to pick it up.

In New York City, it's illegal for a restaurant to call a sandwich a "corned beef sandwich" if it's made with white bread and mayonnaise. ( I agree 100%! )

In California it is illegal to set a mouse trap without a hunting license.

In France, it is against the law to sell an "E.T" doll. They have a law forbidding the sale of dolls that do not have human faces.

In Athens, Greece, a driver's license can be taken away if the driver is thought to be either "poorly dressed" or "unbathed"

In Calgary Alberta, there is still a by-law that requires businesses within the city to provide rails for tying up horses.

In Wilbur, Washington, it is illegal to ride an ugly horse. ( but can you make faces at him? )

In Louisiana, biting someone with your natural teeth is considered "simple assault," but biting someone with your dentures is "aggravated assault."

In the state of Washington, it is illegal to have sex with a virgin under any circumstances. (Including the wedding night.)

In Switzerland, it is illegal for a man to relieve himself while standing up after 10pm.( even with the light on? )

In Florida, it is illegal to fart in a public place after 6 P.M. on Thursdays.

In Massachusetts, it is illegal to go to bed without first having a bath. (However, another law prohibits bathing on Sunday)

In Jidda, Saudi Arabia, women were banned from using hotel swimming pools in 1979.

In Samoa, it's a crime to forget your own wife's birthday...

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Varya’s muscles are barely visible but she has tremendous will-power, translucent body and thread-like tendons.
Varya says, “I wish I could be big, really big: 190 cm tall and weigh more than 100 kg, like my dad.”
Despite the daily workouts, Varya is a top student in her class. Currently, she is in 7th grade

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Holocaust survivors tell love story

In the beginning, there was a boy, a girl and an apple.
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He was a teenager in a death camp in Nazi-controlled Germany. She was a bit younger, living free in the village, her family posing as Christians. Their eyes met through a barbed-wire fence and she wondered what she could do for this handsome young man.

She was carrying apples, and decided to throw one over the fence. He caught it and ran away toward the barracks. And so it began.

As they tell it, they returned the following day and she tossed an apple again. And each day after that, for months, the routine continued. She threw, he caught, and both scurried away.

They never knew one another's name, never uttered a single word, so fearful they'd be spotted by a guard. Until one day he came to the fence and told her he wouldn't be back.

"I won't see you anymore," she said. "Right, right. Don't come around anymore," he answered.

And so their brief and innocent tryst came to an end. Or so they thought.

___

Before he was shipped off to a death camp, before the girl with the apples appeared, Herman Rosenblat's life had already changed forever.

His family had been forced from their home into a ghetto. His father fell ill with typhus. They smuggled a doctor in, but there was little he could do to help. The man knew what was coming. He summoned his youngest son. "If you ever get out of this war," Rosenblat remembers him saying, "don't carry a grudge in your heart and tolerate everybody."

Two days later, the father was dead. Herman was just 12.

The family was moved again, this time to a ghetto where he shared a single room with his mother, three brothers, uncle, aunt and four cousins. He and his brothers got working papers and he got a factory job painting stretchers for the Germans.

Eventually, the ghetto was dissolved. As the Poles were ushered out, two lines formed. In one, those with working papers, including Rosenblat and his brothers. In the other, everyone else, including the boys' mother.

Rosenblat went over to his mother. "I want to be with you," he cried. She spoke harshly to him and one of his brothers pulled him away. His heart was broken.

"I was destroyed," Rosenblat remembers. It was the last time he would ever see her.

___

It was in Schlieben, Germany, that Rosenblat and the girl he later called his angel would meet. Roma Radziki worked on a nearby farm and the boy caught her eye. And bringing him food — apples, mostly, but bread, too — became part of her routine.

"Every day," she says, "every day I went."

Rosenblat says he would secretly eat the apples and never mentioned a word of it to anyone else for fear word would spread and he'd be punished or even killed. When Rosenblat learned he would be moved again — this time to Theresienstadt, in what is now the Czech Republic — he told the girl he would not return.

Not long after, the Russians rolled in on a tank and liberated Rosenblat's camp. The war was over. She went to nursing school in Israel. He went to London and learned to be an electrician.

Their daily ritual faded from their minds.

"I forgot," she says.

"I forgot about her, too," he recalls.

Rosenblat eventually moved to New York. He was running a television repair shop when a friend phoned him one Sunday afternoon and said he wanted to fix him up with a girl. Rosenblat was unenthusiastic: He didn't like blind dates, he told his friend. He didn't know what she would look like. But finally, he relented.

It went well enough. She was Polish and easygoing. Conversation flowed, and eventually talk turned to their wartime experiences. Rosenblat recited the litany of camps he had been in, and Radziki's ears perked up. She had been in Schlieben, too, hiding from the Nazis.

She spoke of a boy she would visit, of the apples she would bring, how he was sent away.

And then, the words that would change their lives forever: "That was me," he said.

Rosenblat knew he could never leave this woman again. He proposed marriage that very night. She thought he was crazy. Two months later she said yes.

In 1958, they were married at a synagogue in the Bronx — a world away from their sorrows, more than a decade after they had thought they were separated forever.

___

It all seems too remarkable to be believed. Rosenblat insists it is all true.

Even after their engagement, the couple kept the story mostly to themselves, telling only those closest to them. Herman says it's because they met at a point in his life he'd rather forget. But eventually, he said, he felt the need to share it with others.

Now, the Rosenblats' story has inspired a children's book, "Angel Girl." And eventually, there are plans to turn it into a film, "The Flower of the Fence." Herman expects to publish his memoirs next year.

Michael Berenbaum, a distinguished Holocaust scholar who has authored a dozen books, has read Rosenblatt's memoir and sees no reason to question it.

"I wasn't born then so I can't say I was an eyewitness. But it's credible," Berenbaum said. "Crazier things have happened."

Herman is now 79, and Roma is three years his junior; they celebrated their 50th anniversary this summer. He often tells their story to Jewish and other groups.

He believes the lesson is the very one his father imparted.

"Not to hate and to love — that's what I am lecturing about," he said. "Not to hold a grudge and to tolerate everybody, to love people, to be tolerant of people, no matter who they are or what they are."

The anger of the death camps, Herman says, has gone away. He forgave. And his life has been filled with love.

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