A household's electricity bills for six months are shown below.

A household's electricity bills for six months…

MediumOriginal question

A household's electricity bills for six months are shown below.

What must the July bill be so that the average for January to July is exactly ₹1,400?

₹1,380Correct answerYour answer₹1,400Correct answerYour answer₹1,420Correct answerYour answer₹1,520Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer D

Correct answer: D

Six-month total = $1{,}240 + 1{,}180 + 1{,}050 + 1{,}320 + 1{,}610 + 1{,}880$ = ₹8,280.
Required seven-month total = $7 \times 1{,}400$ = ₹9,800.
July bill = $9{,}800 - 8{,}280$ = ₹1,520.

Worth noting

The current average is ₹1,380, ₹20 short on each of six months. July must cover $1{,}400 + 6 \times 20$ = ₹1,520, not $1{,}400 + 20$ .

Ten questions from Averages, at your own pace.

Ten questions from Averages, at your own pace.