In need of a math nerd

[Mediocre Man]

I am pretty good at quick math in my head, and have taught my kids many tricks on how to do math quickly in their head. However, my son had a basic 5th grade math question that I could not figure out a trick for, so I was hoping someone might have one.

The question was 117 divided by 13

I know the answer because I did the math long hand, but is there a shortcut for a problem like this?

 

[Denny Crane]

http://www.thinkgeek.com/product/e59d/

 

[BoBoBREWSKI]

Calculator shortcut says 9.

 

[OSUBlazerfan]

You can quickly think of a multiple thats close to 117. 10 comes to mind. 10x13=130
130-117 = 13
10-1 = 9

 

[3RA1N1AC]

yeah find a multiple close to it you know to then add or subtract 13s from it

 

[3RA1N1AC]

like the 99 x whatever bar trick, bet them a beer you can beat a calculator

multiply by 100 and then subtract the original number

 

[BlazerWookee]

I am pretty good at quick math in my head, and have taught my kids many tricks on how to do math quickly in their head. However, my son had a basic 5th grade math question that I could not figure out a trick for, so I was hoping someone might have one.

The question was 117 divided by 13

I know the answer because I did the math long hand, but is there a shortcut for a problem like this?

130-13=117?

 

[e_blazer]

130-13=117?

Math must be hard for Wookees. All that hair covering their fingers and toes.

 

[julius]

You can quickly think of a multiple thats close to 117. 10 comes to mind. 10x13=130
130-117 = 13
10-1 = 9

does that work for other numbers too?

And how did you decide to do 10-1?

 

[3RA1N1AC]

does that work for other numbers too?

And how did you decide to do 10-1?

cant talk for him but it seemed to just happen to work out that way

say 204/17

17 x 10 = 170
17 x 2 = 34
170+34 = 204

204/17 = (10+2)

ive always done math like this in my head, always seemed like the easiest way to me

 

[tlongII]

117+13=130

That tells you the answer is 9 right there.

 

[Hobbesarable]

I am pretty good at quick math in my head, and have taught my kids many tricks on how to do math quickly in their head. However, my son had a basic 5th grade math question that I could not figure out a trick for, so I was hoping someone might have one.

The question was 117 divided by 13

I know the answer because I did the math long hand, but is there a shortcut for a problem like this?

MM, You may like the following site link:
http://mathforum.org/dr.math/

 

[MARIS61]

117 ÷ 13 = 9

 

[barfo]

Very simple trick:

add the digits in the first number (in this case 1+1+7 =9). There's your answer.

There may be some cases where this doesn't work, but there are other tricks you can use then.

barfo

 

[Denny Crane]

Very simple trick:

add the digits in the first number (in this case 1+1+7 =9). There's your answer.

There may be some cases where this doesn't work, but there are other tricks you can use then.

barfo

Quick: what's 17.3 trillion divided by 313.9 million?

 

[Mediocre Man]

Quick: what's 17.3 trillion divided by 313.9 million?

I have no idea, but whatever it is, it would be the same as 17.3 trillion divided by 4 according to barfo

 

[Eastoff]

I have no idea, but whatever it is, it would be the same as 17.3 trillion divided by 4 according to barfo

That's ridiculous, I think you mean divided by 16