Question #47e8d

2 Answers
Jan 23, 2018

28%

Explanation:

If The temperature is 100,
#100# decreased by #60%=40# Degrees
#80% of 40: 32#
#40+32=72#
#100-72=28#
#28%#

Jan 23, 2018

See a solution process below:

Explanation:

First, let's call the initial temperature: #t#

If it first decreased by 60% then the new temperature (#t_n#) would be:

#t_n = t - 60/100t#

#t_n = 100/100t - 60/100t#

#t_n = (100/100 - 60/100)t#

#t_n = 40/100t#

#t_n = 4/10t#

Then if this new temperature increase by 80% the final temperature (#t_f#) would be:

#t_f = t_n + 80/100t_n#

However, we can substitute #4/10t# for #t_n# giving:

#t_f = 4/10t + (80/100 xx 4/10t)#

#t_f = 4/10t + 320/1000t#

#t_f = 400/1000t + 320/1000t#

#t_f = 720/1000t#

#t_f = 72/100t#

Therefore, the final temperature is 72% of the original temperature.

Or, in total the temperature decreased by 28%