Question

The mass of a box measured by a grocer's balance is $2.3kg$. two gold pieces of masses $20.15g$ and $20.17g$ are added to the box. The total mass of the box is:

• A. $2.30kg$
• B. $2.340kg$
• C. $2.34kg$
• D. $2.3kg$

Answer 1

The correct option is D $2.3kg$

Mass of the box measured $m_1=2.3$ $kg$

Mass of the one gold piece $m_2=20.15$ $g$ $=0.02015$ $kg$

Mass of the second gold piece $m_3=20.17$ $g$ $=0.02017$ $kg$

Total mass of the box $M=m_1+m_2+m_3$

$\therefore$ $M=2.3+0.02015+0.02017=2.34032$ $kg$

But as among all the masses, the mass $2.3kg$ contains one significant figure after decimal. So we need to round off the final answer upto one decimal place.

$⟹$ $M=2.3$ $kg$