Paper 1 · Mathematical Reasoning and Aptitude
UGC NET December 2022 (11.03.2023) Shift-II (Sociology)
In a class of 60 students, the average height of 20 students is x centimetres, of another 20 students is y centimetres and of the remaining 20 students is z centimetres. What is the average height of the whole class?
A(x+y+z)/60 cm
B30 cm
C(x+y+z)/20 cm
D(x+y+z)/3 cm ✓ Correct
Correct answer: (D) (x+y+z)/3 cm — The average height of the class is (x+y+z)/3, so the answer is (x+y+z)/3 cm.
Explanation
★The average height of the class is (x+y+z)/3, so the answer is (x+y+z)/3 cm.
★The first 20 students have a total height of 20x.
★The next 20 have 20y and the last 20 have 20z.
★So the total height of all 60 students is 20x plus 20y plus 20z.
★The class average is this total divided by 60.
★That simplifies to (x plus y plus z) divided by 3.
★So the answer is (x+y+z)/3 cm.
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