In August, the ratio of boys and girls in a school's Swimming Club was 3 : 7. In September, 69 new members joined the club. As a result, the ratio of boys to girls in the club became 5 : 4. There were 9 boys in the Swimming Club in August. How many of the new members were girls?
| |
Boys |
Girls |
| Before |
3 u |
7 u |
| Change |
+ 69 |
| After |
5 p |
4 p |
Number of boys at first = 3 u
3 u = 9
1 u = 9 ÷ 3 = 3
Total number of members at first
= 3 u + 7 u
= 10 u
= 10 x 3
= 30
Total number of members in the end
= 30 + 69
= 99
Total number of members in the end
= 5 p + 4 p
= 9 p
9 p = 99
1 p = 99 ÷ 9 = 11
Number of girls in the end
= 4 p
= 4 x 11
= 44
Number of girls at first
= 7 u
= 7 x 3
= 21
Number of new members who were girls
= 44 - 21
= 23
Answer(s): 23
