What number should be placed in the box to help complete the division calculation?

Question

      __53_

  15|7978

     - 7500

         478

       -[    ]

   

 It's 7978 divided by 15 and that blank space under the 478 is what is supposed to be filled in. When I did this I put 465 but I was told it was 450? Thank you.

Answer 1

Long division usually "brings down" one digit at a time, so the 4 result from 79-75 would get just a 7 "tacked on" and we would attempt to divide 15 into 47.  Thus, the 3 is put in the quotient.  The product of 3*15 is 45.

 

But, this problem "brought down" 78 to "tack onto" the 4, and shows 478 as all the rest of the digits of the dividend.  That's o.k. because it may help to position our 45 (if we realize that it really 450) and not get confused as to the important positions of each digit.

 

Now, I say this because 5*15 is just 75, but the process in this problem made it 7500 and subtracted 7978-7500 to get 478, so if you try to divide 15 into 478 you will get 3 for the quotient, and then 450 for the product in the box.  Then, subtract 478-450 to go on with the division.

 

Note:  When you actually work these problems, keeping digits "lined up" (better than this forum allows) is very important.