How many kgs of rice costing Tk 12 per kg must be mixed with 35 kg of rice costing Tk 8 per kg so that may be a gain of 15% by selling the mixture at Tk 12.65 per kg?

Question: How many kgs of rice costing Tk 12 per kg must be mixed with 35 kg of rice costing Tk 8 per kg so that may be a gain of 15% by selling the mixture at Tk 12.65 per kg?

Solution:
Let, the rice of Tk 12 per kg is = x kg
ATQ,
115% of (8 × 35 + 12 × x) = 12.65(35 + x)
⇒ (115/100) × (280 + 12x) = 442.75 + 12.65x
⇒ 322 + 13.8x = 442.75 + 12.65x
⇒ 1.15x = 120.75
⇒ x = 105