问题 解答题

计算下列各式,并将结果用科学记数法表示

(1)(2×103)×(5×10-7

(2)(-2.4×10-5)÷(6×10-3

(3)(1×103)÷(-2×10-8

(4)(1.2×10-42×(5×1022÷(3×10-22

答案

(1)(2×103)×(5×10-7

=(2×5)×(103×10-7

=10×10-4

=10-3

(2)(-2.4×10-5)÷(6×10-3

=-(2.4÷6)×(10-5÷10-3

=-0.4×10-2

=-4×10-3

(3)(1×103)÷(-2×10-8

=(-1÷2)×(103÷10-8

=-0.5×1011

=-5×1010

(4)(1.2×10-42×(5×1022÷(3×10-22

=(1.44×10-8)×(25×104)÷(9×10-4).

=(1.44×25÷9)×(10-8×104÷10-4

=4×1

=4.

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