I need help with a 4th grade probability problem that my grandson asked me about.

Question

Draw a spinner and divide it so that a paper clip will land on R about 1/6 of the time and on B about 1/3 of the time.  The remaining part of the spinner represents Y. About what fraction do you think the clip will land on Y?

Answer 1

If R is 1/6 and B is 1/3 and Y is unknown we break it up into an addition problem.

R + B + Y = the whole

1/6 + 1/3 + Y = 1

Now we need a common denominator.

1/6 + 2/6 + Y = 6/6

Subtract the known amounts from both sides to get Y:

Y = 6/6 - 1/6 - 2/6 = 3/6

Reduce the fraction:

Y = 3/6 = 1/2

Answer 2

A group of people went camping in New Zealand. They will hike from Wellington to Ruapehu. Then they will follow a trail for another 1/2 mile to their campiste. Use a map with scale: 1inch =400 miles as well as class median  step length, and number of steps in 1 minute, to make the following estimate. 1)about How many miles is it from Wellington to ruapehu?