Question 36

Jambmaths question: 

If S = (4t + 3)(t - 2), find ds/dt when t = 5 secs.

Option A: 

50 units per sec

Option B: 

35 units per sec

Option C: 

22 units per sec

Option D: 

13 units per sec

Jamb Maths Solution: 

$\begin{align}  & S=(4t+3)(t-2) \\ & S=4{{t}^{2}}-8t+3t-6 \\ & S=4{{t}^{2}}-5t-6 \\ & \frac{dS}{dt}=8t-5 \\ & \text{When }t=5\text{secs} \\ & \frac{dS}{dt}=[8(5)-5]\text{units per sec} \\ & \frac{dS}{dt}=35\text{units per sec} \\\end{align}$

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