Answer:
5.96 min
Step-by-step explanation:
Jimmy's rate, J = 11 min for whole porch
Amy's rate, A = 13 min for whole porch
to find the combined rate, C,
the reciprocal of the combined rate equals the sum of the reciprocals of each individual rate. i.e
1/C = 1/J + 1/A
substituting the above values
1/C = 1/11 + 1/13 (convert right side to same denominator)
1/C = 13 / (11 x 13) + 11 / (11 x 13)
1/C = 13 /143 + 11 /143
1/C = (13 + 11) /143
1/C = 24 /143 (taking reciprocal of both sides)
C = 143 / 24 = 5.96 min
