Expert: Josh - 2/24/2011

Question
QUESTION: eighty grams of grass seed are used every 100 m^2  of lawn. how many kilograms of grass seed are needed to cover 2000^2 ?

ANSWER: Birdie,

Assuming the units are the same, 2000 m^2 [square meters] is 20 times larger than 100 m^2 [square meters]. So, if 80 grams cover 100 square meters, we would need 20 times that to cover 2000 square meters.

80 x 20 = 1600 gram

Now, since 1000 grams equals 1 kilogram, we need exactly 1.6 kg to do the job.
We get 1.6 from dividing 1600 [gram] by 1000 [gram/kilogram] to get 1.6 [kilogram].

1600 [g]
----------- = 1.6 [kg]
1000 [g/kg]

Cheers

---------- FOLLOW-UP ----------

QUESTION: to check in bags charges $50 for a bag weighing over 23kg, but not more than 32. the charge for a check bag weighing over 32kg, but not more than 45kg is $100.
how much must be paid for three bags weighing 27.9kg 31.5kg and 40.2kg?

Answer
Assuming the contents in each bag cannot be rearranged, here is the answer.

To picture what is going on, draw two intervals representing a scale of weight.

A_________________B_____________________C

Point A reads 23 kg.
Point B reads 32 kg.
Point C reads 45 kg.

First bag is 27.9 kg. This is more than 23 kg and less than 32 kg. So, it is between A and B. This incurs a charge of $50.

Third bag is 40.2 kg. This exceeds 32 kg, but is less than 45 kg. So, it is in the interval between B and C. The charge for this is $100.

It is left as an exercise for you to figure out the charge for the second bag. Just use the same reasoning.

Then, you add up the cost for all 3 bags. Two of which we have already figured out. The cost for the 1st and 3rd bags are $50 and $100, respectively. The cost of the 2nd bag is left for you to work out.