The average weight of 21 boys was recorded as 64 kg. If the weight of the teacher was added, the average increased by 1 kg. What was the teacher's weight?

86 kg

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64 kg

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72 kg

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98 kg

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None of these

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Solution

The correct option is A 86 kg
Here, total weight of 21 boys = 21 $\times$ 64
= 1344 kg
After including the teacher,
total weight = 22 $\times$ 65
= 1430 kg
$∴$ Weight of the teacher = 1430 -1344
= 86 kg
Alternate Method
Weight of teacher = 64 + (21 + 1) $\times$ 1
= 64 + 22 = 86 kg

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The average weight of 21 boys was recorded as 64 kg. If the weight of the teacher was added, the average increased by 1 kg. What was the teacher's weight?

The correct option is A 86 kgHere, total weight of 21 boys = 21 × 64 = 1344 kg After including the teacher, total weight = 22 × 65 = 1430 kg ∴ Weight of the teacher = 1430 -1344 = 86 kg Alternate Method Weight of teacher = 64 + (21 + 1) × 1 = 64 + 22 = 86 kg

The correct option is A 86 kg
Here, total weight of 21 boys = 21 $\times$ 64
= 1344 kg
After including the teacher,
total weight = 22 $\times$ 65
= 1430 kg
$∴$ Weight of the teacher = 1430 -1344
= 86 kg
Alternate Method
Weight of teacher = 64 + (21 + 1) $\times$ 1
= 64 + 22 = 86 kg