Question

Estimate the answers to the following calculations by carrying out order of magnitude calculations.

a) 0.26 x 890
b)
`(1.95)/(0.0067)`
c) 2010 x
`10^(-5)`
d)
`(9.98 x 10^(-4) )/(9 x 10^(2) )`

Answer 1

9514 1404 393

Answer:

a) 230

b) 300

c) 2×10^-2

d) 1.1×10^-6

Explanation:

a) 0.26 × 890 ≈ 1/4 × 900 ≈ 225 ≈ 230

b) 1.95/(.67×10^-2) ≈ 2/(2/3)×10^2 ≈ 300

c) 2010×10^-5 ≈ 2×10^3×10^-5 = 2×10^-2

d) 9.98×10^-4/(9×10^2) = 9.98/9×10^(-4-2) ≈ 1.1×10^-6

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YMMV depending on how you do the rounding and approximate multiplication and division.

The first one can be done multiple ways. For most accurate results, increasing one number while decreasing the other is recommended. (You don't want to compute 0.3×900, for example.)