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The mean age of ten pupils is 12.7
years. Eight pupils are 11, 10, 12, 11,
14, 13, 14 and 16 years old. The ninth ||
pupil is two years younger than the
tenth. What is the age of:
(a) the ninth pupil?
(b) the tenth pupil?

Total age of pupils
= 12.7 x 10
= 127 years

127 - 11 - 10 - 12 - 11 - 14 - 13 - 14 - 16 = 26 ( total age of the other 2 pupils added together )

however, since the ninth pupil is two years younger,

26-2=24
24/2=12 ( age of ninth pupil )
12+2=14 ( age of tenth pupil )

thus, (a) 12 years old,
(b) 14 years old.