In February, the ratio of boys and girls in a school's Robotics Club was 3 : 7. In March, 49 new members joined the club. As a result, the ratio of boys to girls in the club became 5 : 4. There were 15 boys in the Robotics Club in February. How many of the new members were girls?
|
Boys |
Girls |
Before |
3 u |
7 u |
Change |
+ 49 |
After |
5 p |
4 p |
Number of boys at first = 3 u
3 u = 15
1 u = 15 ÷ 3 = 5
Total number of members at first
= 3 u + 7 u
= 10 u
= 10 x 5
= 50
Total number of members in the end
= 50 + 49
= 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 5
= 35
Number of new members who were girls
= 44 - 35
= 9
Answer(s): 9