Ruby bought a watermelon weighing 5 kg 300 g. Out of which she gave 2 kg 680 g to her neighbour. What is the weight of the watermelon left with Ruby?

Weight of watermelon = 5 kg 300 g

= 5 kg + $\dfrac{300}{1000}$ kg = 5 kg + 0.300 kg = 5.300 kg

Weight given to neighbour = 2 kg 680 g

= 2 kg + $\dfrac{680}{1000}$ kg = 2 kg + 0.680 kg = 2.680 kg

Weight left with Ruby = 5.300 - 2.680

Writing in column form and subtracting:

$\begin{array}{r} \phantom{+}5.300 \ -\space 2.680 \ \hline 2.620 \end{array}$

Hence, the weight of the watermelon left with Ruby is 2.620 kg or 2 kg 620 g.