Good evening!

Today we started practicing estimating strategies to help with multiplication. We aren’t using any new strategies this unit. The strategies are the same as our last unit on Whole Numbers. Students will be practicing compatible numbers, compensation, and front-end rounding. Check out some examples below:

Compatible Numbers

Estimate: 78 x 8

Well… 78 is close to 80… and it is an easier number to work with…

So I could solve 80 x 8…

80 x 8 = 640

Therefore 78 x 8 is about 640.

This is an overestimate, because 80 is greater than 78.

Compensation

Estimate: 38 x 52

Well… 38 could be rounded to the nearest 10 and become 40…

Since I rounded 38 up, I need to round 52 down…

52 rounded to the nearest 10 becomes 50…

So I could solve 40 x 50…

40 x 50 = 2000

Therefore 38 x 52 is about 2000.

It is hard to tell if this is an over/under estimate, but compensation is usually an accurate strategy to use.

Front-end Rounding

Estimate: 240 x 4

Well… 240 is already a multiple of 10… but front-end rounding would make it even easier to work with…

When I front-end round, I only keep the first (or the first two) digits…

So… 240 becomes 200…

So I could solve for 200 x 4…

200 x 4 = 800

Therefore 240 x 40 is about 800.

This is an underestimate. Front-end rounding always gives you an underestimate.

Students did a great job working through these examples in their Math groups today. As you can see, a knowledge of multiplication facts is extremely important throughout this unit. Please don’t forget to be practicing your times tables at home as much as possible!

Agenda:

Read 20 minutes

Reading Journal (Friday)

Math: pgs. 86-87 # 1-6, 8-11

Multiplication Quiz – Friday (0x, 1x)

Mathletics – 10 minutes

Mathletics Meet-up: Tomorrow @ 5:30 pm and 7:00 pm

L.A. – Word Practice

Ski Day: Feb. 6th

Emergency Blankets

Thursday – Holiday Hats!