- Adam 160 m/min
- Bernard 120 m/min

Strategy: Put all information in a diagram and draw 'relationships' (with reference to the speed-time-distance formula) to form equations

Since we do not know the distance for the race, let it be

*d*metres.

Since we are not given the time taken by Adam to complete the race, let the time taken be

*t*minutes.

The 2nd diagram shows the position of

**Adam, Bernard and Charlie at**

*t*minutes.Hence, what's common for all three boys is the duration,

*t*minutes.

Using the formula, Distance = Speed x Time

With this, we know that distance covered by Charlie (at t min) = 800

*m*- 250

*m*= 550

*m*

Substitute

*d*= 550 into first equation (i.e. time taken by Adam), we have

Time taken,

*t*= 800 ÷ 150 = 5 minutes

*Hence, Charlie's speed*

= Distance covered/ Time taken

= 550

*m*÷ 5

*min*

=

**110**(Ans)

*m/min*Note: There are other 'shortcuts' to solve the problem. However, the above will give you an idea how to solve the unknown(s) systematically using the known relationships for speed-time-distance.

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