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Units and Measurement

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Question : 12 of 33
Marks: +1, -0
The mass of a box measured by a grocer’s balance is 2.300 kg. Two gold pieces of masses 20.15 g and 20.17 g are added to the box. What is (a) the total mass of the box, (b) the difference in the masses of the pieces to correct significant figures?
Solution:  
Here, mass of the box, m=2.3 kgm=2.3\ \text{kg}
Mass of one gold piece, m1=20.15 gm_{1}=20.15\ \text{g}
=0.02015 kg=0.02015\ \text{kg}
Mass of other gold piece, m2=20.17 gm_{2}=20.17\ \text{g}
=0.02017 kg=0.02017\ \text{kg}
(a) Total mass =m+m1+m2= m + m_1 + m_2
=2.3+0.02015+0.02017= 2.3 + 0.02015 + 0.02017
=2.34032 kg= 2.34032\ \text{kg}
As the result is correct only upto one place of decimal, therefore, on rounding off total mass =2.3 kg= 2.3\ \text{kg}
(b) Difference in masses =m2−m1=m_{2}-m_{1}
=20.17−20.15=20.17-20.15
=0.02 g=0.02\ \text{g}
(correct upto two places of decimal).
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