x = pretul initial
o majorare cu 10% inseamna x×(100%+10%)
o reducere cu 50% inseamna (100% - 20%)
⇒ x × 110/100 × 80/100 = 432 (lei)
x = (432×100×100) / (110×80) = 4320000:8800 ≈ 490,91(lei)
Verificare:
490,91 × 110 / 100 ≈ 540(lei)
540 × 80/100 = 432(lei) (adevarat)