How much 20 mangoes cost if the of 12 such type is Rs 144?

Then, the cost of 12 mangoes = Rs 144

$$\therefore \frac{\text{Cost of 20 mangoes}}{\text{Cost of 12 mangoes}} = \frac{x}{144}$$

$$ \frac{20}{12} = \frac{x}{144}$$

$$ \frac{5}{3} = \frac{x}{144}$$

Multiplying both sides by 144

$$ 5 \times 144 = 3x$$

$$ 720 = 3x$$

Dividing both sides by 3

$$ \frac{720}{3} = x$$

$$ 240 = x$$

Hence, the cost of 20 mangoes is Rs 240.