Question

Q16. The speed limit on a road is 40mph.
A scooter drives 9 miles in 13 minutes. Is the scooter breaking the speed limit?​

Answer 1

Step-by-step explanation:

Yes: we’re comparing 9/13 miles per minute to the limit of 40/60=2/3 miles per minute.

Multiply both by 13*3; now we’re asking if 9*3 is larger than 2*13. The answer is yes: 27>26. So we’re breaking the speed limit.

If you want to avoid calculation, you can alternatively rewrite 2/3 miles per minute as 8/12 miles per minute. Now both speeds are part of the sequence

1/4, 2/5, 3/6, 4/7, 5/8, 6/9, …

Note that this sequence is monotonically increasing (since the derivative of x/(x+4) is positive, if you want a proof), so 9/13 is larger than 8/12.

In general, for 0≤p<q and any positive number a , we have p+aq+a>pq .

Answer 2

Answer:Yes

Step-by-step explanation:  He is breaking the speed limit because 9miles in 13 minutes will give you a speed limit of 41.54mph

HOW: 13minutes to hours is 13/60 = 0.2167hours

Speed= $\frac{d}{t}$

= $\frac{9}{0.2167} = 41.54$mph