John had
35 as many cards as Cathy. After John bought another 4 cards, he had 10 less cards than Cathy. How many cards did John have at first?
| |
John |
Cathy |
| Before |
3 u |
5 u |
| Change |
+ 4 |
|
| After |
3 u + 4 |
5 u |
Cathy had 10 more cards than John in the end. So, if John had another 10 cards, he would have the same number of cards as Cathy.
5 u = 3 u + 4 + 10
5 u - 3 u = 4 + 10
2 u = 14
1 u = 14 ÷ 2 = 7
Number of cards that John had at first
= 3 u
= 3 x 7
= 21
Answer: 21
