Rashim lent ₹ 600 to Geeta for 2 yr and ₹ 150 to Seeta 4 yr and received altogether ₹ 80 as simple interest from both. Find the rate of interest.

Given. T₁ = 2 yr and T₂ = 4 yr,
P₁ = 600, P₂ = 150.
According to the question,
SI₁ + SI₂ = 80
[(600 x R x 2)/100] + [(150 x R x 4)/100] = 80
⇒ 120R + 60R = 800
⇒ 180R = 800
∴ R = 800/180 = 80/18 = 40/9
= 4⁴/₉%