Sean had twice as many balls as David. After David lost 10 balls and Sean bought 10 balls, Sean had 4 times as many balls as David. How many balls did Sean and David have altogether at first?
| |
Sean |
David |
Total |
| Before |
2x5 =
10 u |
1x5 =
5 u |
3x5 =
15 u |
| Change |
+ 10 |
- 10 |
|
| After |
4x3 =
12 u |
1x3 =
3 u |
5x3 =
15 u |
The number of balls that David lost and bought is the same. So, the total number of balls remains unchanged. Make the total number of balls the same. LCM of 3 and 5 is 15.
Number of balls that Sean bought
= 12 u - 10 u
= 2 u
2 u = 10
1 u = 10 ÷ 2 = 5
Number of cards that they had altogether at first
= 15 u
= 15 x 5
= 75
Answer(s): 75
