In May, the ratio of girls and boys in a school's Robotics Club was 3 : 7. In June, 24 new members joined the club. As a result, the ratio of girls to boys in the club became 5 : 4. There were 9 girls in the Robotics Club in May. How many of the new members were boys?
| |
Girls |
Boys |
| Before |
3 u |
7 u |
| Change |
+ 24 |
| After |
5 p |
4 p |
Number of girls 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 + 24
= 54
Total number of members in the end
= 5 p + 4 p
= 9 p
9 p = 54
1 p = 54 ÷ 9 = 6
Number of boys in the end
= 4 p
= 4 x 6
= 24
Number of boys at first
= 7 u
= 7 x 3
= 21
Number of new members who were boys
= 24 - 21
= 3
Answer(s): 3
