Significant Figures when first multiplying numbers then adding?

Question

such like (34.512X2.43)+5.6

Would you multiply the two numbers together and use significant figures for that result then add 5.6 and use significant figures again for the final answer? Or would you multiply the two numbers then add and only use signficant figures at the end?

Answer 1

Each case if different. when doubt, carry an extra digit.

in your example, use 3 digits are good for the entire calculation. You can round the answer to 2 if you want.

Subtraction is a more difficult case, as you can subtract two similar numbers and lose significance.

eg  27(10005 - 10003)

if you used 2 places throughout, you would get 0 as an answer.

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