How many children
Number Theory
Level
2
The average height of a group of children would be increased by 5 cm if 10 of the children in the group were each 10 cm taller. How many children are in the group?
15
16
21
20
18
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1 solution
Average height of the group of children= N u m b e r o f c h i l d r e n i n t h e g r o u p S u m o f H e i g h t s o f t h e c h i l d r e n
Therefore, the average height of the group of children increases by 5cm if the sum of the increases in the heights of the children, divided by the number of children in the group is equal to 5.
If 10 of the children in the group were each 10cm taller, then the sum of the increase in the heights of the children would be 10 x 10=100 cm
Thus, 100 divided by the number of children in the group equal to 5. We know that 2 0 1 0 0 =5.
Hence the number of children in the group equal to 20.