GMAT math thinking skills 5

 

Topic: Time and work

Difficulty level: Moderately difficulty

You will get word problems like this in your exams.

The concepts involved in this problem are

1. Time and work

2. Ratios

3. Equations

Method 1

This method will take time as you need to read the question,  write equations, and solve them. Time consuming!!

Alex takes 6 days to a work. Amount of work done by Alex in 1 day = 1/6

 Bill takes 10 days to a work. Amount of work done in 1 day = 1/10

 Charles takes 15 days to a work. Amount of work done in 1 day = 1/15

 

Method 2

This method is faster. We can use percentages to solve. 

Alex completes 100% of work in 6 days. Bill completes 100% of work in 10 days. Charles completes 100% of work in 15 days.

 In 2 days Alex completes

 Lets construct a table

Days          Percentage

6                100%

2                  ??

 

Cross multiplying = 2x100/6 =33.33 %

In 2 days Alex completes =33.33% of work

 

Similarly

Bill completes 100% of work in 10 days.

In 2 days Bill completes 20% of the work

 

 

Charles completes 100% of work in 15 days.

In 2 days Bill completes 13.33% of the work

 

Total work completed = 33.33 +20 +13.33= 66.66%

 

Remaining work = 100-66.66 = 33.33% 

 

 Charles completes 100% of work in 15 days.

In how many days he will complete 33.33%

 

Percentage             Days

100%                        15

33.33                        ??

 

Cross multiplying

= 33.33x15 / 100  = 5 days

 Take away: 

 You can use percentages as a tool to save time and minimize calculations.

Watch this tutorial video and understand mathematical reasoning skills..

You can excel in math once you learn these skills.