The average height of some boys is 123 cm. When 3 girls, with a total height of 333 cm, are included, the average height if the children becomes 120 cm. How many children are there altogether?
|
Boys |
Girls |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
123 |
|
120 |
Total value |
123 u |
333 |
120 u + 360 |
Total height of the boys
= 1 u x 123
= 123 u
Total height of the children = 123 u + 333
123 u + 333 = 120 u + 360
123 u - 120 u = 360 - 333
3 u = 27
1 u = 27 ÷ 3 = 9
Total number of children
= 1 u + 3
= 9 + 3
= 12
Answer(s): 12