19 of the guests at a concert hall were boys. 90% of the remaining guests were girls and the rest were adults. The number of girls was 459 more than the total number of boys and adults. After some girls left the concert hall, 75% of the guests that remained were girls. How many girls left the concert hall?
Boys |
Adults |
Girls |
Total |
1x5 |
8x5 |
9x5 |
|
1x4 |
9x4 |
|
5 |
4 |
36 |
45 |
|
Boys and adults |
Girls |
Before |
9x1 = 9 u |
36x1 = 36 u |
Change |
|
- 9 u |
After
|
1x9 = 9 u |
3x9 = 27 u |
90% =
90100 =
910 Adults : Girls = 1 : 9
The total number of adults and girls at first is repeated. Make the total number of adults at first the same. LCM of 8 and 10 is 40.
75% =
75100 =
34 When some girls left, the total number of boys and adults remains unchanged. Make the total number of boys and adults the same. LCM of 9 and 1 is 9.
The number of girls was 459 more than the total number of boys and adults at first.
Number of more girls than the total number of boys and adults at first
= 36 u - 9 u
= 27 u
27 u = 459
1 u = 459 ÷ 27 = 17
Number of girls who left the concert hall
= 36 u - 27 u
= 9 u
= 9 x 17
= 153
Answer(s): 153