Harry, Jeremy and Oliver had 120 cards. After Harry used 11 cards and Jeremy used
13 of her cards, Harry had twice as many cards left as Jeremy. Oliver bought another 21 cards, he had thrice the number of cards Jeremy had left. How many cards did Oliver have at first?
| |
Harry |
Jeremy |
Oliver |
Total |
| Before |
4 u + 11 |
3 u |
6 u - 21 |
120 |
| Change |
- 11 |
- 1 u |
+ 21 |
|
| After |
4 u |
2 u |
6 u |
|
Comparing Harry
and Jeremy in the end |
2 |
1 |
|
|
Comparing Oliver
and Jeremy in the end |
|
1 |
3 |
|
Number of cards that Harry had in the end
= 2 x 2 u
= 4 u
Number of cards that Oliver had in the end
= 3 x 2 u
= 6 u
Total number of cards at first
= 4 u + 11 + 3 u + 6 u - 21
= 13 u - 10
13 u - 10 = 120
13 u = 120 + 10
13 u = 130
1 u = 130 ÷ 13 = 10
Number of cards that Oliver had at first
= 6 u - 21
= 6 x 10 - 21
= 60 - 21
= 39
Answer(s): 39
