A new harvesting machine works twice as fast as an old one. The old machine takes 30 days to harvest a farm. How many days does the new machine take?

15 daysCorrect answerYour answer30 daysCorrect answerYour answer45 daysCorrect answerYour answer60 daysCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer A

Correct answer: A

Twice as fast means twice the work per day.
So it needs half the time: $30 \div 2 = 15$ days.

Worth noting

Time and efficiency are inversely related: double the speed, half the days. 60 days multiplies instead of dividing, and 45 days adds 50% instead of halving.

Concept: Efficiency is inversely proportional to time
Typical timeTypical: 40 s
Your timeYours: —

The rule this testsEfficiency and wages

Practise this chapter →

Ten questions from Time & Work, at your own pace.

A new harvesting machine works twice as fast as an old one. The old machine takes 30 days to harvest a farm. How many days does the new machine take?

Explanation