Question

Robert and Elaine ran around the high school track during gym class. robert ran 1/2 of the way around the track in 5/6 minute. Later in the day, elaina ran 3/4 of the way around the track in 9/10 minute. When they meet after school, Robert claims that he can run father in a minute than elaina. Is he correct or incorrect?Explain your reasoning.
Unpack the problem:



Make a plan:



Solution:



Look back and explain:

Answer 1

Answer

Incorrect

Explanation

Unpack the problem:

Let the distance round the track to be X.

Speed is the ratio of distance to time.

Robert run a distance of (1/2)x

Elaine run a distance of (3/4)x

Make a plan:

Finding the speed of each.

Compare their speeds to determine who ran faster than who.

Solution:

Robert's speed =(1/2)x/(5/6)

=1/2×6/5x

= (3/5)x

= 0.6x

Elaine's speed = (3/4)x/(9/10)

= (3/4)×(10/9)x

= (5/6)x

= 0.83333x

Elaine ran faster than Robert.

Look back and explain:

0.83333x > 0.6x

Elaine's speed is higher than Robert's speed.

This shows that Elaine ran faster than Robert.