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 40 g	$1.30	$0.70
	Every additional 10 g or part thereof	$0.25

How much did Risa pay for the postage when she sent a letter which weighed 86 g and 6 postcards to Korea by airmail?
Remaining mass that Risa had to pay for the letter as it was more than 40 g
= 86 - 40
= 46 g

Number of sets of additional 10 g of the letter that Risa had to pay for 
= 46 ÷ 10
= 4 r 6

Total number of sets of additional 10 g of the letter that Risa had to pay for 
= 4 + 1
= 5

Amount that Risa had to pay for the sets of additional 10 g of the letter
= 5 x 0.25
= $1.25

Total amount that Risa had to pay for the letter
= 1.30 + 1.25
= $2.55

Amount that Risa had to pay for the 6 postcards
= 6 x 0.70
= $4.20

Total amount that Risa paid
= 2.55 + 4.20
= $6.75

Answer(s): $6.75