At the concert, there were 77 less boys than girls. After
25 of the boys and
57 of the girls had left the hall, there was an equal number of boys and girls that remained behind. Find the number of boys who were present at the concert at first.
|
Boys |
Girls |
Less |
Before |
5x2 = 10 u |
7x3 = 21 u |
11 u |
Change |
- 2x2 = - 4 u |
- 5x3 = - 15 u |
|
After |
3x2 = 6 u |
2x3 = 6 u |
|
Fraction of boys that remained
= 1 -
25 =
35 Fraction of girls that remained
= 1 -
57 =
27 The number of boys and girls in the end is the same. Make the number of boys and girls in the end the same. LCM of 3 and 2 is 6.
3x25x2 Boys =
2x37x3 Girls
610 Boys =
621 Girls
Total boys at first = 10 u
Total girls at first = 21 u
Number of less boys than girls at first
= 21 u - 10 u
= 11 u
11 u = 77
1 u = 77 ÷ 11 = 7
Number of boys at first
= 10 u
= 10 x 7
= 70
Answer(s): 70