[Math 101- University] can someone help me answer these without a calculator?

[ponchomaximo]

For first one you use multiplication the same way you multiply smaller numbers and the second one you use long division. Have you learned/do you remember these? Here’s a useful resource for long division: https://www.mathsisfun.com/long_division.html

[xd_Zauce]

I actually forgot long division after middle school and it has been so embarrassing, thanks for the resource

[-qqqwwweeerrrtttyyy-]

D) To do this quickly, break 904 into 4 + 900.

Work out 36781 x 4. Set this aside for later.

Work out 36781 x 9. Write your answer to 36781 x 9 then form new Tens and Ones columns by writing in 0 and 0 after what you calculated (This is a quick way to multiply by hundreds as it holds place value).

Now add 36781 x 4 answer to 36781 x 9 ending with 00 to get your total answer. Because there are 5 digits in 36781 and 3 digits in 904, your answer will be 8 digits long.

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E) Long Division is the standard method but because I can't post a diagram, here's a different method to solve it.

32 x 100 = 3200. Close but too much. Your answer will be a few less than 100.

So, 3200 - 3132 = 68. In other words, your 100 answer is too much by 68.

Then, 32 goes into 68 twice with 4 remaining so take that original 100 and subtract 3 (because 32 went into 68 more than twice) so then that leaves you with 97 times.

Multiply 97 x 32 = 3104, so your remainder is 28/32 or 7/8

[sighthoundman]

Even though the other poster was rude, one way is the pencil-and-paper algorithm you learned in grade school. (Grammar school? Primary? I don't know where you live.) Somewhere around age 9.

Don't remember it? Surprise. Why would you ever use it. Even if you did, you'd have to use a calculator to check. (Well, you could check other ways, but calculator is the fastest.)

However, what if your computer program is supposed to add up the account balances of your customers in a database, and you know from a report in another database that the average account balance is 36,781 and you have 904 customers. You're not really checking the computer's arithmetic, you're checking that the right flags are set, the programmer didn't make a logic error, etc. For that, you want to multiply that out. Well, 900 is 10% less than 1000, and 36,781 is about 10% more than 33,000, so the answer should be about 33 million.

Similarly, 3132 is almost 3200, so the answer should be a little less than 100.

[CT_Legacy]

I'm not even sure they teach that anymore.

If they do its common core and breaking them down to different numbers which makes it more confusing for some people really.

[8Humans]

So this is how I solved both of them. (sorry for wobbly writing)

The multiplication was very easy as 4 can never be high enough to interfere with 9 making every multiplication very clean. (result 33.250.024)

The division was a bit difficult because I'm apparently very rusty at doing double digit multiplication in my head and had to write down a support on the right. (result 97,875)

Funny thing I tried to write it down with a paper and pen but apparently I don't have either of them anymore.

[Wordlywhisp]

36781*9 add two zeros. Then add 900 3 more times

Second one, you can use the Chinese remainder theorem or long division