Using the magic triangle for speed, distance and time (compound measures)
Speed Triangle Video
Speed, distance and time can be calculated using a magic triangle. D (the distance) goes in the top of the triangle, S (speed) goes in the bottom left of the triangle and T (time) goes in the bottom right of the triangle.
If you want to calculate the speed cover up S in the triangle and you get S = D/T
If you want to calculate the time cover up T in the triangle and you get T = D/S
If you want to calculate the distance cover up D in the triangle and you get D = S×T
A car covers a distance of 150 miles in 2 ½ hours. Calculate the average speed of the car in miles per hour.
Since you want the speed cover up S in your triangle and you get S = D/T
Next substitute D = 150 and T = 2.5 into the formula for speed:
S = D/T
S = 150/2.5 = 60mph
A car is travelling at a constant speed of 80kmph. How many kilometres will the car cover if it keeps this speed for the next 3 hours and 15 minutes?
This time you need to work out the distance so D = S × T
Be careful with the time as it needs to rewritten in hours only. 15 minutes is ¼ hour (0.25) so 3 hours and 15 minutes is 3.25 hours.
Now substitute S = 80 and T = 3.25 into the formula for distance:
D = S ×T
= 80 × 3.25
So the car travels 260km in 3 hours and 15 minutes.
How long will it take Simon to jog a distance of 15 miles if Simon jogs at a steady speed of 6mph.
Here you need to calculate the time so T = D/S.
Now substitute D = 15 and S = 6 into the formula T = D/S
T = 15/6
T = 2.5 hours
So Simon will take 2 hours and 30 minutes to cover the distance.
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