Questions on standard form

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Express this number in standard form:
3,700,000,000,000,000,000,000

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Express this number in standard form:
0.000 000 000 55

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What is 3 x 10¹² x 8 x 10^-2?

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6 x 10²³ atoms of carbon weigh 12g. How much does one atom weigh, in kg?

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A beach is 10km long and 1km wide. The average depth of the sand is 2 metres. If an average grain of sand fits in a volume of 10^-9 cubic metres, how many grains of sand are there on the beach?

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If it takes 2 seconds to count every grain of sand, and if there are 2 x 10⁷ seconds for counting in each year (allowing time for sleep and eating), how many years would it take to count all the grains on the beach in the last question?