6.2+Using+Rules+of+Thumb+0910

M.M 15/01/10

=Many important practical and mathematical applications involve comparing quantities of one kind or another; it is important to know which method to use and how we should use them.=

6.2

A) //It takes about 100 maple trees to make 25 gallons of maple syrup.// Mr. Paulo made maple syrup from all of his sugar maple trees. He ended up with 16 gallons of syrup. About how may sugar maple trees does he need?

ans: 25 gallons = 100 trees 1 gallon = __100__ 25 = 4 trees 16 gallons = 4 x 16 = 64 maple trees.

B) //A 5 minute shower requires about 18 gallons of water//. About how much water do you use for an 8 minute shower? How much water will you use if you take an 8 minute shower every day of the year?

ans: 5 minutes = 18 gallons 1 minute = __18__ 5 = 3 8 minute = __18__ 5 x 8 = 28.8 gallons 28.8 x 365 = 10512 gallons a year

C) //A double spaced page of text contains about 250 words if it is printed in Times with a font size of 12, and about 330 words if it is printed in Times with the font size of 10.// Jeremy printed his term paper in the computer lab. He used 10 - point Times and the paper came to 15 double spaced pages. Jeremy's teacher requires term papers be 20 double spaced pages long. If Jeremy changes the font to the 12 - point Times, how long will his paper be?

ans: 10 points - 15 double spaced 1 - point __15 3__ 10 = 2 12 - points 15 10 x 12 = 18 double spaced

D) //Jogging// burns 100 per mile. Elizabeth jogs at a rate of 4.5 miles per hour. How long will it take her to burn 1200 - calorie lunch she ate at Burger Heaven?

ans: 1 mile - 100 calories 4.5 - 100 x 4.5 = 450 450 - __4.5__ 450 1200 - __4.5__ 450x 1200 = 12 miles

6.2 Follow Up

Ask adults you know if they use rules of thumb in their jobs or at home. Write down one of the rules you learn. Write a problem that can be solved using the rule.

ans: Since 2 quarts are 4 pints of milk. Then how many is 1 quart?

2 quarts - 4 pint 1 quarts - 4 2 = 2

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