Q. 124.2( 33 Votes )
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?
Mass of the box (m): 2.300 Kg (2 significant figures, 1 after decimal)
Gold pieces: G1 = 20.15 g = 0.02015 Kg (4 significant figures) and G2 = 20.17 g = 0.02017 Kg (4 significant figures)
(a) total mass of box (M) = m + G1 + G2
M = 2.300 + 0.02015 + 0.02017 = 2.34032 Kg but in addition the final result should have significant digits after decimal equal to the minimum number of significant digits of all the numbers used.
Therefore, M = 2.3 Kg (upto 2 significant digits and 1 after decimal due to 1 significant digit in m)
(b) difference in the masses = G2 – G1 = 0.02 g (1 significant digit). In subtraction the final result should have significant digits after decimal equal to the minimum number of significant digits of all the numbers used.
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