Suresh played 80 hours of tennis last week. This week Suresh played 50% less tennis. How many hours of tennis did Suresh play this week?

1 Answer
Mar 7, 2017

Answer:

Suresh played 40 hours of tennis this week

Explanation:

The formula for determining the percentage change or rate of change is:

#p = (N - O)/O * 100# Where:

#p# is the percentage change: -50 for this problem
#N# is the New Value: what we will solve for in this problem
#O# is the Old Value: 80 hours for this problem

Substituting and solving for #N# gives:

#-50 = (N - 80)/80 *100#

#color(blue)(80)/color(red)(100) xx -50 = color(blue)(80)/color(red)(100) xx (N - 80)/80 *100#

#-4000/color(red)(100) = cancel(color(blue)(80))/cancel(color(red)(100)) xx (N - 80)/color(blue)(cancel(color(black)(80))) *color(red)(cancel(color(black)(100)))#

#-40 = N - 80#

#-40 + color(red)(80) = N - 80 + color(red)(80)#

#40 = N - 0#

#40 = N#

#N = 40#