Mary and Roshel collected buttons. Roshel gave 70% of her buttons to Mary. As a result, Mary's buttons increased by 20%. If Mary had 420 buttons left, find the total number of buttons the two girls had at first.
| |
Comparing the change
in Roshel's buttons |
Roshel |
Mary |
| Before |
10x1 =
10 u |
|
5x7 =
35 u |
| Change |
- 7x1 =
- 7 u |
- 1x7 =
- 7 u |
+ 1x7 =
+ 7 u |
| After |
3x1 =
3 u |
|
6x7 =
42 u |
70% =
70100 =
710 20% =
20100 =
15 The number of buttons that Mary gave to Roshel is repeated. Make the number of buttons that Mary gave to Roshel the same. LCM of 1 and 7 is 7.
Number of buttons that Mary had in the end = 42 u
42 u = 420
1 u = 420 ÷ 42 = 10
Number of buttons that Roshel and Mary had at first
= 10 u + 35 u
= 45 u
= 45 x 10
= 450
Answer(s): 450
