Solve the problem.
-Frank can type a report in 4 hours and James takes 7 hours. How long will it take the two of them typing together?
A) $\frac { 11 } { 28 } \mathrm { hr }$
B) $7 \mathrm { hr }$
C) $\frac { 28 } { 3 } \mathrm { hr }$
D) $\frac { 28 } { 11 } \mathrm { hr }$

Question

Solve the problem.
-Frank can type a report in 4 hours and James takes 7 hours. How long will it take the two of them typing together? 
A) $\frac { 11 } { 28 } \mathrm { hr }$
B) $7 \mathrm { hr }$
C) $\frac { 28 } { 3 } \mathrm { hr }$
D) $\frac { 28 } { 11 } \mathrm { hr }$

Quizplus · Accepted Answer

Frank's rate is $1/4$ report per hour, and James's rate is $1/7$ report per hour. Together, they type $(1/4 + 1/7) = (7/28 + 4/28) = 11/28$ report per hour. To complete 1 report, it takes $1 / (11/28) = 28/11$ hours.

Solve the Problem 1128hr\frac { 11 } { 28 } \mathrm { hr }2811​hr

Solve the Problem $\frac { 11 } { 28 } \mathrm { hr }$