Standard Mathematics Primary 5 Average

The average mass of 4 boys is 35 kg. When a 5th boy joins the group, the new average mass becomes 36 kg. What is the mass of the 5th boy?

A 36 kg
B 40 kg
C 35 kg
D 39 kg
Show Worked Solution

Worked Solution

Step 1: Total mass of 4 boys = 4 × 35 kg = 140 kg. Step 2: Total mass of 5 boys = 5 × 36 kg = 180 kg. Step 3: Mass of the 5th boy = Total mass of 5 boys - Total mass of 4 boys Step 4: 180 kg - 140 kg = 40 kg. Answer: 40 kg

Correct answer: 40 kg

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