# Video: KS2-M16S • Paper 3 • Question 9

The mass of a 10p coin is 6.5 g. The mass of a 5p coin is half the mass of a 10p coin. What is the mass of the six coins altogether in grams?

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### Video Transcript

The mass of a 10p coin is 6.5 grams. The mass of a 5p coin is half the mass of a 10p coin. What is the mass of the six coins altogether in grams?

So we know that a 10p coin has a mass of 6.5 grams. And the mass of a 5p coin is half the mass of a 10p coin. Half of 6.5 is 3.25 grams. So now we know the mass of a 10p coin and a 5p coin.

There are three 10p coins. So we need to calculate the mass of three coins by multiplying 6.5 by three. Six times three is 18, and 0.5 times three is 1.5. So the mass of three 10p coins is 19.5 grams.

There are also three five-pence coins. We calculated the mass of one 5p coin to be 3.25 grams. So we need to multiply this by three to find the mass of three coins. Three times three is nine, and three times 0.25 is 0.75. So the total mass of three 5p coins is 9.75 grams.

The question asks us what the mass of all six coins is altogether. Finally, we can add our two totals together to give us the total mass of all six coins. 19.5 doesn’t have a digit in the hundredths. You could add a zero as a placeholder if it helps. Zero plus five is five. Five plus seven is 12. Nine plus nine is 18, plus the one we exchanged 19. And one plus the one we exchanged gives us a total of two. The mass of all six coins is 29.25 grams.