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

Destination	Letters		Postcards
	Mass	Postage Rate	Per piece
Korea, Japan	1st 20 g	$1.10	$0.70
	Every additional 10 g or part thereof	$0.40

How much did Anna pay for the postage when she sent a letter which weighed 45 g and 2 postcards to Korea by airmail?
Remaining mass that Anna had to pay for the letter as it was more than 20 g
= 45 - 20
= 25 g

Number of sets of additional 10 g of the letter that Anna had to pay for 
= 25 ÷ 10
= 2 r 5

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

Amount that Anna had to pay for the sets of additional 10 g of the letter
= 3 x 0.40
= $1.20

Total amount that Anna had to pay for the letter
= 1.10 + 1.20
= $2.30

Amount that Anna had to pay for the 2 postcards
= 2 x 0.70
= $1.40

Total amount that Anna paid
= 2.30 + 1.40
= $3.70

Answer(s): $3.70