Hello VickyI make the answer about 68.

70 mph = feet per sec

So in 20 sec the train passes over thirty-foot sections, which is a bit more than 68.

I make it just over 30%.In attempting to calculate the carrying capacity of a cylindrical pipe, Avery measured the outer diameter to be 2 inches, neglecting to notice that the pipe was one eighth of an inch thick. By what percent did Avery overestimate the carrying capacity of the pipe?

24%

Thanks.

Vicky.

The inner diameter is inches. The carrying capacity is proportional to the area of the cross-section, which in turn is proportional to the square of the diameter. So by using 2 in instead of 1.75 in, the area is overestimated in the ratio , or by a factor of (3 d.p.)

So Avery has overestimated by about 30.6%

Grandad