1. Estimating Products and Quotients
September 10, 2009

2. Rounding
You can estimate either a product or a quotient by first rounding each number to its greatest place value.
Example A Example B
8,659 x / 29
9,000 x 100= / 30=
900,

3. Compatible Numbers
You can estimate using compatible numbers, which are close to the actual numbers, but are easier to solve.
Example A Example B
x / 48
25 x 40= / 50= 1,

4. Range
You can estimate by finding a range. When you find a range, the exact answer is between the two estimates.
Example:
X 687
Round both numbers to the lesser Round both numbers to the greater 100
300 x 600=180, x 700= 280,000
Underestimate Overestimate
So the product 342 x 687 is between 180,000 and 280,000!

5. Practice with Rounding
X 9,031=
6,238 / 76=
/ 87=
489 x 2,970=

6. Practice with Compatible Numbers
X 9,031=
6,238 / 76=
/ 87=
489 x 2,970=

7. Practice with Range
X 9,031=
6,238 / 76=
/ 87=
489 x 2,970=