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625 sats \ 9 comments \ @Scroogey 9h science

This was part of today's homework for a 14 year old, who found it a little tricky:

Laura's older sister shares her comic books with her siblings. Every child should get 4 books less than the number of children. Since two of the children don't like comic books, the remaining children get one additional book each. How many children and how many comic books are there?

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0 sats \ 4 replies \ @Scroogey OP 8h

Since it was solved so quickly, here's the most difficult one in the set (it was marked as difficult, and not mandatory), which made me fetch pen and paper:

How old is Jimmy? Tom is 24 years old. He is twice as old as Jimmy was when Tom was as old as Jimmy is now.

100 sats \ 2 replies \ @SimpleStacker 8h

Jimmy was 12 when Tom was as old as Jimmy is now.

Thus, Jimmy is 18 now, because 6 years ago Jimmy was 12 and Tom was 18.

I did guess and check again, haha.

67 sats \ 1 reply \ @Scroogey OP 8h

That's correct, but again there is an equation to be found and solved :)

There are two points in time, now and then.

We define

x

as Jimmy's age now. "Then" is when Tom was

x

years old.

Person	Now	Then
Tom	24	x
Jimmy	x

To get from now to then (reading Tom's line) we subtract 24 and add x, hence the bottom right cell is

x-24+x = 2x-24

Person	Now	Then
Tom	24	x
Jimmy	x	2x-24

Now the equation is simply

2 \times (2x - 24) = 24

, or

x = 18

10 sats \ 0 replies \ @SimpleStacker 8h

Haha I basically stumbled upon my answer as I was trying to figure out what the right equation is

0 sats \ 0 replies \ @noknees 2h

I was as old as 18 when I was Jimmy's age.

500 sats \ 2 replies \ @SimpleStacker 9h

Seems like the best way forward is to guess and check. The solution is 6 children and 12 books. That way when they're evenly divided among 6, they each get 2 books (4 less than the number of children.) When divided among 4, the four get 3 books (1 more than they'd otherwise get).

42 sats \ 1 reply \ @Scroogey OP 8h

There is a way without trying, but building the equation was the tricky part (solving it is simple).

Let's define

x

as the number of children. Every child should get

x-4

books, and there are

x \times (x-4)

books. The number of books freed by the 2 children who don't like them is

2 \times (x-4)

. That's the same number as are given to the remaining children i.e.

(x-2) \times 1

. Hence,

2 \times (x-4) = (x-2) \times 1

x = 6

10 sats \ 0 replies \ @SimpleStacker 8h

I initially tried to build two equations with two unknowns,

b

and

c

, but they didn't come out linear, so rather than mess with more algebra I resorted to guess and check instead.

10 sats \ 0 replies \ @winteryeti 8h

Kids don't read books these days. They look at their smartphones and iPads.