kotela wrote:

How many hours did it take helen to drive from her house to her parent's house?

1. Helen's average speed on this trip was 72 Km/hr

2. If Helen's average speed on this trip had been 8 Km/hr greater it would have taken 1 hr less

can anyone explain?

let time req. be t.

let distance covered be d.

1.

d/t=72.

Insufficient

2.

d/(t-1)=80

Insufficient

1+2

d=72t

d=80(t-1)

72t=80(t-1)

Sufficient

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