- Estimation is the process of arriving at an approximate answer.
- A case of pop, which contains 24 cans, is $4.98 on sale. What is the price per can?
change 4.98 to 5.00 or 500 pennies
Change 24 to 25
500 pennies 1 case 20 pennies
------------ x -------- = ------------
1 case 25 cans cans
This will be low, since we added another can, but it is an estimate.
The real price is
498 pennies 1 case 498 pennies
----------- x ------- = ------------ = 20.75
1 case 24 cans 24 cans
Check your work
( 25x20 = 500)
- The basic technique of estimation is rounding
- The rules for rounding are simple.
- Pick a digit you want to round to
- Look at the digit to the right
- If this digit is less than 5 do nothing
- If this digit is 5 or more, add one to the digit to be rounded
- Change all digits to the right of the digit to be rounded to 0
Round 47.23 to the nearest one
7 is the digit to be rounded
2 is the digit to the right, this is less than 5 so do nothing
47 is the answer
Round 639.82 to the nearest Tens.
3 is the digit to be rounded
9 is the digit to the right, this is greater than 5 so add 1 to 3
640 is the answer
Round 29741 to the nearest hundreds
9 is the digit to be rounded
7 is the digit to the right, it is greater than 5 so add 1
30000 is the answer.
- Knowing the digit to round to is the important part. Why did I round
to 25 and 500 in the above example?
- Could I have rounded to 30 and 500?
- When we are estimating we want to be as accurate as we need to be, but make the computation easy.
- If I wanted to take everyone here out to lunch at Burger King, how much money should I have?
How many people are in the room? (37? -> 40)
How much is lunch at Burger King? (4.78 -> 5.00)
So I better have 40 people x$5/person = $200,
nope I guess that's not going to happen
- If I take the Wife and Kids to lunch at Georgio's, and we order meals costing:
6.74 -> 7.00
7.32 -> 7.00
6.94 -> 7.00
4.34 -> 4.00
and four drinks at $1.35 each. -> 5.00
Estimate the total
25+5 = 30
15% tip = 4.5
10% tax = 3.0 or about $38
- Will this be the actual bill?
- Why would I want to estimate this bill?
- How much money does the University make on this class?
Again there are about 40 people in the class.
In-state tuition is $204 per credit hour (or $200)
This is a 3 credit hour class.
40 people 3 credits $200 $200x3x40
--------- x --------- x ---------- = --------- = $24,000/class
class 1 person 1 credit class
- Reading pi charts.