Ali paints twice as fast as Bain. This means A = 2B. We have 2 equations now. Can we calculate C? No. No equation has C up till now.

Now Carlos joins them making the combined rate A+B+C. This rate has the value 6000 over 5, which is 1200.

Can we calculate C now? Can you use the 1st equation in the 3rd in any way? Yes!

We can substitute 1000 in place of A+B. So, we get 1000+C=1200. This means that C = 200.

So, Carlos paints 200 sq. ft. per hour. To answer the question: how much can be paint in 2 hours? That’s right! 400 sq. ft. This is the answer.

Note that we did not use the 2nd equation at all.

Question 3:-Pause here and read the question.

This question concerns weights of apples, oranges and potatoes. And none of these weights are known. So, let’s assign symbols to these unknowns:

Let A be weight of one apple, O be weight of one orange and P be the weight of one potato. So, we need to find the value of A to answer this question. Let’s take a look at what information the question contains.