The average height of some boys is 120 cm. When 3 girls, with a total height of 306 cm, are included, the average height if the children becomes 114 cm. How many children are there altogether?
|
Boys |
Girls |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
120 |
|
114 |
Total value |
120 u |
306 |
114 u + 342 |
Total height of the boys
= 1 u x 120
= 120 u
Total height of the children = 120 u + 306
120 u + 306 = 114 u + 342
120 u - 114 u = 342 - 306
6 u = 36
1 u = 36 ÷ 6 = 6
Total number of children
= 1 u + 3
= 6 + 3
= 9
Answer(s): 9