Question

After how much time to the nearest minute Will the cost of plan a be equal to the cost of plan b

Answer 1

Let

y ----> total charge in a month

x ----> number of minutes

so

Plan A

y=0.21x+11

Plan B

y=0.10x+20

Equate both equations

0.21x+11=0.10x+20

solve for x

0.21x-0.10x=20-11

0.11x=9

x=9/0.11

x=81.82 minutes

Convert to hours and minutes

81.82 minutes=60+21.82=1 hour 22 min

therefore

the answer is option A