Pre-lab Assignment 1. Student A measures an object and records a value of 1.5 cm. Student B measures the same object
and records a value of 1.50 cm. They have both done their measurements correctly. Why do these
measurements differ?
a. They aren't different.
b. Person A used a ruler with markings every 0.1 cm. Person B used a ruler with markings every
0.01 cm.
c. Person A used a ruler with markings every 1 cm. Person B used a ruler with markings every 0.1
cm.
d. Person A rounded their measurement.
2. When multiplying or dividing measured numbers, we use the measurement with the least number of
significant figures to determine the number of significant figures (sf) in our answer. For example:
3.5 cm x 4.75 cm - 17 cm? (even though the calculator gives 16.675) Solve the following problems
assuming all are measured numbers. Report the correct number of significant figures.
a. 7.00 x 15.00 =
b. 40.2.1.901 =
c. (0.003)(13.2) =
d. 1.590+ 0.3975 =

1. d. Person A rounded their measurement

2) a. 105.

b. 76.4

c. 0.04

d. 1.988

Explanation:

1. Measuring an object is done with the least precise one. Person A recorded 1.5cm while Person B recorded 1.50cm of the same object. This measurement differs in the sense that Person A rounded up their measurement to 2 significant figures (1.5) while Person B recorded their answer as three significant figures (1.50).

2. During multiplication and division, the result is written as the measurement in the lowest significant figure.

a. 7.00 x 15.00 = 105. Calculator showed 105.00, which is 5 s.f (two zeros after decimal point are significant). The least significant figure is 3, hence 105.00 is rounded up to 105.

b. 40.2.1.901 = 76.4; The calculator answer of this operation is 76.420200 but since the lowest significant figure is 3. We round up our answer to 3 s.f i.e. 76.4

c. (0.003)(13.2) = 0.04. For this operation, calculator answer is 0.0396, however, the lowest significant figure in the question is 1 i.e. 0.003. Note that the two zeros before 3 are insignificant. Hence, our answer will be rounded up to 1 s.f i.e. 0.04

d. 1.590+ 0.3975 = 1.988. the calculator answer to this operation is 1.9875. However, the least significant figure in the question is 4 i.e. 1.590. hence, the answer will be rounded up to 4 s.f which is 1.988.

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