Question

Fatima wants to mail three parcels to three village schools. She finds that the postal charges are Rs 20, Rs 28 and Rs 36, respectively. If she wants to buy stamps only of one denomination, what is the greatest denomination of stamps she must buy to mail the three parcels?

Answer 1

The postal charges to mail three parcels are ₹ 20, ₹ 28 and ₹ 36 respectively.

Also, Fatima wants to buy stamps only of one denomination.

So, to find the greatest denomination of stamps, we find the HCF of 20, 28 and 36.

2	20
2	10
5	5
	1

 

2	28
2	14
7	7
	1

 

2	36
2	18
3	9
3	3
	1

Now, 20 = 2 × 2 × 5

28 = 2 × 2 × 7

36 = 2 × 2 × 3 × 3

∴ The HCF of 20, 28 and 36 is 2 × 2 = 4

So, ₹ 4 is the greatest denomination of stamps, she must buy to mail the three parcels.