Sunday, March 10, 2013

Adding pounds and tons.

Question:  One brick weighs 2 1/4 tons.  A second brick weighs 300 pounds.  What is the weight of the brick in pounds?  What is the weight of the brick in simplest form in tons?

Answer:  A ton is 2000 pounds.  1/4 ton is (1/4) x 2000 = 500.     the total number of pounds for the two bricks is 2000+500+300 = 2800.

To get the number of tons divide the number of pounds by 2000.   The number of tons  is 2800/2000 but this is clearly not in simplest form.

The easiest way to get the fraction in simplest form is to lob off two zeros from both the numerator and the denominator.  Basically we are dividing both the numerator and denominator by 100.

2800/2000 = 28/20

Dividing by 20

1 8/20

Dividing both the numerator and denominator of the fraction part by 4 we get 8/20=2/5.

 Our answer is the two bricks weigh 1 2/5 tons.    this is the same as 1.4.  (Can you confirm this.)


Note:  I tried to answer the question in the easiest way.  One could have  converted 300 pounds to tons and added to 1 1/4 tons but this would have taken longer.  We could have simplified 2800/2000 by dividing the numerator and denominator by common prime factors but when you have zeros at the end of both the numerator and the denominator it is best  to divide by the factor of 10.


You should always try to solve the math problem in the easiest possible way.  Of course initially it is not always obvious which way is easiest.    this will become easier with practice.  

No comments:

Post a Comment