Salman purchases 7 kg 670 gm of potatoes and 3 kg 42 gm of onions and some tomatoes. Find the weight of tomatoes (in kg) if he purchases a total of 12 kg of vegetables.

The correct option is A 1.288
Weight of potatoes = 7 kg 670 gm
= 7 kg + 670 gm
= 7 kg+ $\frac{670}{1000}\text{kg}$
$(\because 1\text{kg}=1000\text{gm})$
= 7 kg + 0.67 kg
= 7.67 kg
Similarly,
weight of onions = 3 kg + $\frac{42}{1000}\text{kg}$
= 3 kg + 0.042 kg = 3.042 kg
Since the total weight of vegetables is 12 kg, we have:
Weight of tomatoes = 12 kg - Weight of potatoes - Weight of onions
= 12 kg - 7.67 kg - 3.042 kg
= 1.288 kg