# U.S. History 1877-Present 9.8: Hiroshima and Nagasaki

Once Germans figured out how to split a uranium atom, the American bomb building business was suddenly booming.

Language | English Language |

U.S. History | U.S. History 1877-Present |

### Transcript

But it’s always a chore figuring out how much carroturkey to cook for so many hungry tummies.

The Rabbits have 49 children, and there are 37 grandchildren per child.

How many total children and grandchildren are there? [Maths long multiplication problem]

To solve a problem like this, you’ll need to use long multiplication. [Students working in class]

Don’t be deceived by the name though.

In fact, it’s actually a bit of a shortcut.

Rather than adding up the grandkids for all 49 children…

…long multiplication will allow us to quickly determine the total number of mouths there are to feed. [Bunny chewing food]

When else might you need to use long multiplication?

Suppose you have 15 people to buy Christmas presents for, and you plan to spend $25 on each person.

Long multiplication will be handy for figuring out how big a dent this is going [Girl using a calculator]

to put in your checking account.

All right, so back to the Rabbit family.

If there are 49 children and each has 37 kids of their own,

we can multiply 49 by 37 to get the number of grandchildren.

To solve, we’re going to work backwards through 37’s digits… [Man gesturing to cars walking backwards]

…first multiplying by 7…

…then multiplying by the 3 in the tens place, which is actually 30.

So first, we need to find 49 times 7.

7 times 9 is 63. Write the 3, carry the 6.

7 times 4 is 28, plus the carried 6 is 34.

When we write down 34… we get 343.

Next multiply 3 by 49.

Repeat the steps we just did, multiplying 3 by 49, but this time write a zero before [Bunny hops up the stairs]

you begin, since our 3 is actually a 30.

3 times 49 comes out to 147, so we get 1,470.

Next add 343 plus 1,470.

3 plus 0 equals 3.

4 plus 7 equals 11, so we write 1 and carry the other 1.

3 plus 4 plus the carried 1 equals 8. And 1 plus nothing equals… 1.

That means there are 1,813 grandkids…but don’t forget we still have to add the 49 kids. [Jack and Bunny's children and grandchildren]

Well, we get 1,813 plus 49….3 plus 9 is 12… write the 2, carry the 1… 1 plus 4 plus the carried

1 gives us 6…and we can drop down the 1 and the 8…

…to give us 1,862 total kids and grandkids with tummies a-rumblin’.

We really don’t envy Jack and Bunny.

Especially at tax time. It must be a nightmare trying to claim that many dependents. [Jack and Bunny in the kitchen with the kids and grandkids]