In October, the ratio of boys and girls in a school's Computer Club was 4 : 7. In November, 35 new members joined the club. As a result, the ratio of boys to girls in the club became 5 : 4. There were 20 boys in the Computer Club in October. How many of the new members were girls?
|
Boys |
Girls |
Before |
4 u |
7 u |
Change |
+ 35 |
After |
5 p |
4 p |
Number of boys at first = 4 u
4 u = 20
1 u = 20 ÷ 4 = 5
Total number of members at first
= 4 u + 7 u
= 11 u
= 11 x 5
= 55
Total number of members in the end
= 55 + 35
= 90
Total number of members in the end
= 5 p + 4 p
= 9 p
9 p = 90
1 p = 90 ÷ 9 = 10
Number of girls in the end
= 4 p
= 4 x 10
= 40
Number of girls at first
= 7 u
= 7 x 5
= 35
Number of new members who were girls
= 40 - 35
= 5
Answer(s): 5