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 40 g	$1.10	$0.60
	Every additional 10 g or part thereof	$0.20

How much did Risa pay for the postage when she sent a letter which weighed 102 g and 7 postcards to Vietnam by airmail?
Remaining mass that Risa had to pay for the letter as it was more than 40 g
= 102 - 40
= 62 g

Number of sets of additional 10 g of the letter that Risa had to pay for 
= 62 ÷ 10
= 6 r 2

Total number of sets of additional 10 g of the letter that Risa had to pay for 
= 6 + 1
= 7

Amount that Risa had to pay for the sets of additional 10 g of the letter
= 7 x 0.20
= $1.40

Total amount that Risa had to pay for the letter
= 1.10 + 1.40
= $2.50

Amount that Risa had to pay for the 7 postcards
= 7 x 0.60
= $4.20

Total amount that Risa paid
= 2.50 + 4.20
= $6.70

Answer(s): $6.70