How Accurate Are These Sig Fig Calculations and Unit Conversions?

[cbrowne]

Hey I don't want to loose points for this primary question, could someone please go over my answers. Thanks!

Homework Statement

1. Perform the following operations and write your answers with appropriate
number of significant figures: (a) 589.01−89.020 (b) 1.0×9.00 (c) 180 /pi
(d) 180.0 /pi (e)3.901x10^-5+ 1.0x10^-7

2. Perform the following unit conversions and express the answer in scientific
notation: (a) 0.510 kg to g (b) 92 mi to km (c) 3 0.50 m to 3 cm (d) 15 μs to ms
(e) 60.0 km/h to m/s

The Attempt at a Solution

a) 589.01-89.020 = 499.99
b) 1.0 x 9.00 = 9.0
c) 180/ Π = 57
d) 180.0/Π = 57.30
e) 3.901 x 10^-5 + 1.0 x 10^-7 = 0.00004


2. a) 0.510kg x 1000g/1kg= 5.1 x 10²g

b) 92 mi x 1.609344km/1mi= 1.48059 x 10² km

c) 0.50m³ x 1 000 000cm³/ 1m³ = 5 x 10⁵ cm³

d) 15μs x 1ms/0.001 μs = 1.5 x 10^-2ms

e) 60.0km/1hour = 65000m/3600 sec = 1.805556 x 10¹ m/s

 

[Joskoplas]

1e looks reeaall suspicious.

If I multiplied both numbers by 10^7 (for my convenience), I'd see 390.1 + 1.0

I don't have to convert it back to the proper decimal place to see there's a problem with saying 400