Home work help?

Question

There were some exercise books and files in a box. The number of exercise books was twice the number of files. Each time 7 exercise books and 5 files were taken out of the box. After a while, only 30 exercise books were left.
(a) How many files were taken out?
(b) What was the total number of exercise books and files in the box at first?

*Pls do not use algebra to solve the question. thks for all help!

Answer 1

Just start adding 7 to 30 and 5 to 0 until the books are double the files.
37, 5
44, 10
51, 15
58, 20
65, 25
72, 30
79, 35
86, 40
93, 45
100, 50 <------- Beginning amounts

Therefore 50 files were taken out.

Answer 2

Without algebra??? Hmmm.. and are you sure you have all the info, because there could be infinite solutions. I guess maybe we should look for the first? Ok...

Okay, go backwards, staring at 30 exercise books. We need to find a point, I guess the first possible point, where the number of exercise books is twicw the number of files. And since the starting number of exercise books was twice the number of files yet were reduced 7 at a time, we need only lok at the times when the number of exercise books was even - in other words, every other time of removal. so..

books files
30 . .17
44 . .22

So 44 and 22, total of 66, appears to be the minimum, assumming books and files were removed at least once.

I'll ask again, are you sure you provided all the info? Answers above assume that at the end, there were 0 files left - is that the case?

Answer 3

Let the initial number of files be 100.then,there were initially 200 of exercise books
Each time 5 files were takenout.
Hence to take out all the files ,they have to be tken out 100/5 or 20 times
If the exercise books and files wee taken out twenty times.then 20*7 or 140 exercise books were taken out
No of exercise books left
=200-140
=60
But actually,the number of exercise books left were 30
Hence the initial no of exercise books were
(30/60)*200=100
Therefore
(b)total no. of exercise books were 100 and the number of files were 100/2=50
(a) 50 files were taken out.

Answer 4

At the end there were 30 Exercise Books and zero files.
Prior to that there were 37 Ex Books and 5 files
Prior to that there were 44 Ex Books and 10 files
Prior to that there were 51 Ex Books and 15 files
Prior to that there were 58 Ex Books and 20 files
Prior to that there were 65 Ex Books and 25 files
Prior to that there were 72 Ex Books and 30 files
Prior to that there were 79 Ex Books and 35 files
Prior to that there were 86 Ex Books and 40 files
Prior to that there were 93 Ex Books and 45 files
Prior to that there were 100 Ex Books and 50 files
So 50 files were taken out
Tota Ex Books and files in box originally was 150

Answer 5

How can you solve it without using algebra?

Answer 6

no algebra...?

then no.