In a classroom the average height of all the boys was 170 cm. Rahim recently joined the class which originally had 20 boys increased the average to 171cm. Then find the height of Rahim.
185 cms
191 cms
190 cms
none
Explanation:
Before Rahim joined the total height of all the boys = 170 X 20 = 3400.
New average = (Total height of all students + height of Rahim)/21 = 180
Therefore (3400 + height of Rahim)/21 = 171
Therefore height of Rahim = 3780 - 3400 = 191 cms.