In July, the ratio of boys and girls in a school's Robotics Club was 2 : 5. In August, 21 new members joined the club. As a result, the ratio of boys to girls in the club became 4 : 3. There were 6 boys in the Robotics Club in July. How many of the new members were girls?
| |
Boys |
Girls |
| Before |
2 u |
5 u |
| Change |
+ 21 |
| After |
4 p |
3 p |
Number of boys at first = 2 u
2 u = 6
1 u = 6 ÷ 2 = 3
Total number of members at first
= 2 u + 5 u
= 7 u
= 7 x 3
= 21
Total number of members in the end
= 21 + 21
= 42
Total number of members in the end
= 4 p + 3 p
= 7 p
7 p = 42
1 p = 42 ÷ 7 = 6
Number of girls in the end
= 3 p
= 3 x 6
= 18
Number of girls at first
= 5 u
= 5 x 3
= 15
Number of new members who were girls
= 18 - 15
= 3
Answer(s): 3
