maths form 2

2009-07-26 8:20 pm

there are about 148900000 km of land on Earth. On 20th July 2004,the Earth population just reached 6481 milloin.

(a)By rounding off the given numbers correct to 2 significant figures ,estimate
(i)the number of people on each km of land;
(ii)how many m of land each man on Earth can occupy.

回答 (1)

賣女孩的火柴

2009-07-26 9:44 pm

✔ 最佳答案

In the question, "km" should be "km^2",
and similarly "m" should be "m^2".

Area of land
= 148900000 km^2
≈ 1.5 x 10^8 km^2 (2 sig. figs.)
= 1.5 x 10^14 m^2 (2 sig. figs.)

Number of people
= 6481 x 10^6 people
≈ 6.5 x 10^9 people (2 sig. figs.)

(i)
The number of people on each km of land
= (6.5 x 10^9 people) / (1.5 x 10^8 km^2)
= [(6.5/1.5) x 10] people/km^2
= 43 people/km^2 (2 sig. figs)

(ii)
Area of land each man on Earth can occupy
= (1.5 x 10^14 m^2)/(6.5 x 10^9 people)
= [(1.5/6.5) x 10^5] m^2/people
= 23000 m^2/people (2 sig. figs.)

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