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

Destination	Letters		Postcards
	Mass	Postage Rate	Per piece
Indonesia, Malaysia	1st 30 g	$0.90	$0.40
	Every additional 10 g or part thereof	$0.35

How much did Olivia pay for the postage when she sent a letter which weighed 79 g and 2 postcards to Indonesia by airmail?
Remaining mass that Olivia had to pay for the letter as it was more than 30 g
= 79 - 30
= 49 g

Number of sets of additional 10 g of the letter that Olivia had to pay for 
= 49 ÷ 10
= 4 r 9

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

Amount that Olivia had to pay for the sets of additional 10 g of the letter
= 5 x 0.35
= $1.75

Total amount that Olivia had to pay for the letter
= 0.90 + 1.75
= $2.65

Amount that Olivia had to pay for the 2 postcards
= 2 x 0.40
= $0.80

Total amount that Olivia paid
= 2.65 + 0.80
= $3.45

Answer(s): $3.45