A can write 3 notebooks in 48 days and B can write 4 notebooks in 48 days .…
2024
A can write 3 notebooks in 48 days and B can write 4 notebooks in 48 days . If, with the help of their friend C , they write 5 notebooks in 20 days , then C alone can write 5 notebooks in days
- A.
48
- B.
49
- C.
45
- D.
47
Attempted by 539 students.
Show answer & explanation
Correct answer: A
Answer: 48 days.
Key steps: compute individual daily rates and use rates to find the friend's time.
A's rate: A writes 3 notebooks in 48 days → A's rate = 3/48 = 1/16 notebook per day.
B's rate: B writes 4 notebooks in 48 days → B's rate = 4/48 = 1/12 notebook per day.
A + B rate = 1/16 + 1/12 = 7/48 notebook per day.
Together with the friend they write 5 notebooks in 20 days → combined rate = 5/20 = 1/4 notebook per day. The friend's rate = 1/4 − 7/48 = 5/48 notebook per day.
Time for the friend to write 5 notebooks = 5 ÷ (5/48) = 48 days.