Eric Nicholas K's answer to syjiaxuan's Secondary 4 A Maths Singapore question.
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Here is the relevant Desmos plot for the graph.
If PB = x m, then AP = (90 - x) m and PQ = ./ (x^2 + 1600) m.
Since he can run from A to P at a speed of 8 m/s, time taken to travel from A to P
= Distance / Time
= (90 - x) / 8 s
Since he can run from P to Q at a speed of 6 m/s, time taken to travel from P to Q
= Distance / Time
= [./ (x^2 + 1600) ] / 8 s
Their sum is the total time taken. In any case the minimum point of the graph is located at x = 45.356. It follows that the distance AP = 90 - x = 44.644 m.
Something is not exactly right with the given solution of x = 24.6 m.
If PB = x m, then AP = (90 - x) m and PQ = ./ (x^2 + 1600) m.
Since he can run from A to P at a speed of 8 m/s, time taken to travel from A to P
= Distance / Time
= (90 - x) / 8 s
Since he can run from P to Q at a speed of 6 m/s, time taken to travel from P to Q
= Distance / Time
= [./ (x^2 + 1600) ] / 8 s
Their sum is the total time taken. In any case the minimum point of the graph is located at x = 45.356. It follows that the distance AP = 90 - x = 44.644 m.
Something is not exactly right with the given solution of x = 24.6 m.
Date Posted:
4 years ago
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