The table shows the airmail rates for sending letters and postcards to some countries.

Destination	Letters		Postcards
	Mass	Postage Rate	Per piece
Thailand, Vietnam, Myanmar	1st 20 g	$0.90	$0.60
	Every additional 10 g or part thereof	$0.45

How much did Usha pay for the postage when she sent a letter which weighed 48 g and 3 postcards to Thailand by airmail?
Remaining mass that Usha had to pay for the letter as it was more than 20 g
= 48 - 20
= 28 g

Number of sets of additional 10 g of the letter that Usha had to pay for 
= 28 ÷ 10
= 2 r 8

Total number of sets of additional 10 g of the letter that Usha had to pay for 
= 2 + 1
= 3

Amount that Usha had to pay for the sets of additional 10 g of the letter
= 3 x 0.45
= $1.35

Total amount that Usha had to pay for the letter
= 0.90 + 1.35
= $2.25

Amount that Usha had to pay for the 3 postcards
= 3 x 0.60
= $1.80

Total amount that Usha paid
= 2.25 + 1.80
= $4.05

Answer(s): $4.05