David has 90% as many cards as Valen. If David gives away 50% of the cards and Valen gives away 10% of his cards, they will have 135 cards altogether. How many cards do the two of them have?
| |
David |
Valen |
Total |
Comparing David
and Valen at first |
9x2 =
18 u |
10x2 =
20 u |
|
| Before |
2x9 =
18 u |
10x2 =
20 u |
|
| Change |
- 1x9 =
- 9 u |
- 1x2 =
- 2 u |
|
| After |
1x9 =
9 u |
9x2 =
18 u |
135 |
90% =
90100 =
910 50% =
50100 =
12 10% =
10100 =
110 The number of cards that David has at first is repeated. Make the number of cards that David has the same. LCM of 9 and 2 is 18 u.
The number of cards that Valen has at first is repeated. Make the number of cards that Valen has the same. LCM of 10 and 10 is 20 u.
Number of cards in the end
= 9 u + 18 u
= 27 u
27 u = 135
1 u = 135 ÷ 27 = 5
Total number of cards that the two of them have
= 18 u + 20 u
= 38 u
= 38 x 5
= 190
Answer(s): 190
