Jack has 90% as many stamps as Tom. If Jack gives away 50% of the stamps and Tom gives away 20% of his stamps, they will have 250 stamps altogether. How many stamps do the two of them have?
| |
Jack |
Tom |
Total |
Comparing Jack
and Tom at first |
9x2 =
18 u |
10x2 =
20 u |
|
| Before |
2x9 =
18 u |
5x4 =
20 u |
|
| Change |
- 1x9 =
- 9 u |
- 1x4 =
- 4 u |
|
| After |
1x9 =
9 u |
4x4 =
16 u |
250 |
90% =
90100 =
910 50% =
50100 =
12 20% =
20100 =
15 The number of stamps that Jack has at first is repeated. Make the number of stamps that Jack has the same. LCM of 9 and 2 is 18 u.
The number of stamps that Tom has at first is repeated. Make the number of stamps that Tom has the same. LCM of 10 and 5 is 20 u.
Number of stamps in the end
= 9 u + 16 u
= 25 u
25 u = 250
1 u = 250 ÷ 25 = 10
Total number of stamps that the two of them have
= 18 u + 20 u
= 38 u
= 38 x 10
= 380
Answer(s): 380
