an experienced bricklayer can work twice as fast as an apprentice bricklayer. Af

Question

an experienced bricklayer can work twice as fast as an apprentice bricklayer. After they work together on a job for 6 h, the experienced bricklayer quits. The apprentcie requires 10 more hours to finish the job.. How long would it take the experienced bricklayer working alone to do the job?

Explanation / Answer

Let x = number of bricks per hour laid by the apprentice. So, 2x is the number of bricks laid by the experienced bicklayer. Working together for 6 hours, they lay (2x+x) bricks in an hour, so after 6 hours... 6(2x+x) --> 6(3x) --> 18x. Then the apprentice is left to finish the work, taking 10 hours --> 10x bricks in total. So, the job laid 18x + 10x bricks --> 28x. Now, the question says how many hours would it take the experienced bricklayer to lay this many bricks? Well, his rate is 2x and the number of hours is the unknown...call it y --> 2xy. And this has to equal the total from the first way: 28x. Therefore, 2xy = 28x 2y = 28 y = 14 hours

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