Tom had 100 more erasers than Andy. Tom gave 20% of his erasers to Andy. Andy in return gave 50% of his erasers to Tom. In the end, Andy had 318 less erasers than Tom. How many erasers did Tom have at first?
| |
Tom |
Andy |
Comparing Tom
and Peter at first |
100 more |
|
| Before |
5 u + 100 |
5 u |
| Change 1 |
- 1 u - 20 |
+ 1 u + 20 |
| After 1 |
4 u + 80 |
6 u + 20 |
| Change 2 |
+ 3 u + 10 |
- 3 u - 10 |
| After 2 |
7 u + 90 |
3 u + 10 |
20% =
20100 =
1520% x 100
=
20100 x 100
= 20
50% x 20
=
50100 x 20
= 10
50% x 6 u
=
50100 x 6 u
= 3 u
Andy had 318 less erasers than Tom in the end. If another 318 erasers are given to Andy, both will have the same number of erasers.
7 u + 90 = 3 u + 10 + 318
7 u - 3 u = 10 + 318 - 90
4 u = 238
1 u = 238 ÷ 4 = 34
Number of Andy's erasers at first
= 5 u
= 5 x 34
= 170
Answer: 170
