A real world problem for inequalities

Question

The answer has to be 8.5

Answer 1

EXAMPLE QUESTION

A planet’s distance from its sun is estimated to vary between about 91,140,000 and 94,860,000 miles. If the speed of light in space is about 186,000 miles per second, express as an inequality the time in minutes for light from the sun to reach the planet.

SOLUTION

distance=speed×time, time=distance/speed.

If t is the time in minutes, then the time in seconds is 60t, so:

91140000/186000≤60t≤94860000/186000,

490≤60t≤510,

490/60≤t≤510/60,

49/6≤t≤17/2,

8.17≤t≤8.5 minutes.