Relative capacity: B is 80% more than A Tap B’s capacity is 80% greater than A’s. If both run together, they fill the tank in 45 hours. How long would B take alone to fill the tank?

Introduction / Context:
“80% more” means B’s rate is 1.8 times A’s rate. With the joint time known, we solve for the base rate and then get B’s solo time by inversion.

Given Data / Assumptions:

• Together time = 45 h ⇒ combined rate = 1/45 per hour.
• Let A’s rate = r; then B’s rate = 1.8r = 9r/5.

Concept / Approach:
r + 9r/5 = 1/45 ⇒ solve for r. Then B-alone time = 1 / (9r/5).

Step-by-Step Solution:

Verification / Alternative check:
1/126 + 1/70 = (5 + 9)/630 = 14/630 = 1/45.

Why Other Options Are Wrong:
72, 66, 48 contradict the derived rate ratio 1 : 1.8.

Common Pitfalls:
Treating “80% more” as 1.8 more (i.e., 2.8×) instead of 1.8× the base.

Final Answer:
70 h