Opal and Sarah collected cards. Opal gave 10% of her cards to Sarah. As a result, Sarah's cards increased by 70%. If Opal had 378 cards left, find the total number of cards the two girls had at first.
| |
Opal |
Sarah |
Comparing the change
in Sarah's cards |
| Before |
10x7 =
70 u |
|
10x1 =
10 u |
| Change |
- 1x7 =
- 7 u |
+ 1x7 =
+ 7 u |
+ 7x1 =
+ 7 u |
| After |
9x7 =
63 u |
|
17x1 =
17 u |
10% =
10100 =
110 70% =
70100 =
710 The number of cards that Opal gave to Sarah is repeated. Make the number of cards that Opal gave to Sarah the same. LCM of 1 and 7 is 7.
Number of cards that Opal had in the end = 63 u
63 u = 378
1 u = 378 ÷ 63 = 6
Number of cards that Opal and Sarah had at first
= 70 u + 10 u
= 80 u
= 80 x 6
= 480
Answer(s): 480
