If 40% of A = B and 30% of B = C, then 20% of (A + C) is:

Concept: Percentage-of relationships translate into ratios — if p% of X equals Y, then X = Y ÷ (p/100), i.e. X is expressed as a multiple of Y. When several quantities are linked this way, express every quantity in terms of ONE common variable before combining them, since percentages compound multiplicatively, not additively.

1. "40% of A = B" means 0.4A = B, so A = B ÷ 0.4 = 2.5B.

2. "30% of B = C" means C = 0.3B directly.

3. Add A and C, both now expressed in terms of B: A + C = 2.5B + 0.3B = 2.8B.

4. Take 20% of this combined value: 0.2 × 2.8B = 0.56B.

5. Express 0.56B as a percentage of B: 0.56B = 56% of B.

Cross-check: Substituting a concrete number confirms this. Let B = 100. Then A = 100 ÷ 0.4 = 250 (check: 40% of 250 = 100 = B ✓), and C = 30% of 100 = 30. So A + C = 250 + 30 = 280, and 20% of 280 = 56 — which is 56% of B = 100. ✓