Question

Ginny works twice as fast as Sunny. If Ginny takes 3 hours to finish a work, then how much time will Sunny and Ginny together take to finish a work twice as large?

• A. 2 hours
• B. 4 hours
• C. 2.5 hours
• D. 3.5 hours

Answer 1

The Correct Option is B

Work Rate Calculation 

- Let the total work required to finish be W.

- If Ginny takes 3 hours to finish the work, Ginny’s rate of work is:

\[ \text{Ginny's rate} = \frac{W}{3} \text{ work per hour} \]

- Sunny works half as fast as Ginny, so Sunny’s rate of work is:

\[ \text{Sunny's rate} = \frac{W}{6} \text{ work per hour} \]

- Together, their combined rate of work is:

\[ \text{Combined rate} = \frac{W}{3} + \frac{W}{6} \]

Taking the LCM of 3 and 6:

\[ \text{Combined rate} = \frac{2W}{6} + \frac{W}{6} = \frac{3W}{6} = \frac{W}{2} \]

- To complete work twice as large (2W), the total time required is:

\[ \text{Time} = \frac{2W}{\frac{W}{2}} = 4 \text{ hours} \]

Conclusion: Sunny and Ginny together will take 4 hours to finish the work twice as large.

The correct answer is (b) 4 hours.