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Question P6 Same time, same distance

PSLE 2012 — Bakery and library

A bakery and a library are 120 m apart. They are located between Hong's house and Jeya's house. The bakery is exactly half-way between the two houses. One day, Hong and Jeya started cycling from their houses at the same time and they arrived at the library together. Jeya cycled at 70 m per min while Hong cycled at a speed 15 m per min faster than Jeya.

  1. (a) How much further did Hong cycle than Jeya?
  2. (b) How far is Jeya's house from the library?

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About this method

Same time, same distance

Two travellers spend the same time, or cover the same distance.

In this one. Riding for the same length of time makes the two distances share one unit, so they are in the ratio of the speeds (70 : 85 = 14 : 17); the bakery being the mid-point puts the library 120 m off centre, which makes the two rides differ by 240 m — and that difference is exactly the 3-unit gap.

the same time for bothfasterslowerthe gap grows by 2 shares per hour

How to spot it

Two travellers set off together or one chases another, with constant speeds and a question about who is ahead, when they meet, or how far apart they are.

Common mistake

Children divide the whole distance by the difference in speed instead of dividing the gap between the travellers, or compare distances covered over different lengths of time.

Practise a similar question

Standard Aladdin and Jasmine were having a race on their magic flying carpets. They left the same starting point for the market at 13 00. Both of them did not change their speed throughout the journey. Aladdin travelled at a cons…
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