Math Focus 2
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# Surf for More Math

## CHAPTER 2: NUMBER TO 50

### Lesson 5: Representing Numbers in Different Ways

Use these interactive activities to encourage students to have fun on the Web while learning about the numbers to 50. Students can try these activities on their own or in pairs.

Goal

Use benchmarks of 10 and 5 to locate numbers on a rekenrek.
Describe a two-digit numeral in different ways.
[C, ME, R, V]

Instructions for Use

Rekenrek allows students to practice identifying amounts on a rekenrek for numbers up to 20.

To use Rekenrek, click on    for a rekenrek with 10 beads or on    for a rekenrek with 20 beads.  A number of beads on the rekenrek is shown. Click on one of the numbers from 1 to 20 that matches the number of beads shown. A bar on the right keeps score – red for incorrect answers and green for correct answers. When 10 pictures are complete, a final score is shown. Click “new” to repeat the activity or “stop” to end the activity.

Electronic Abacus is an interactive applet that allows students to explore how to use an abacus for representing and adding numbers.

To Use Electronic Abacus, click “Entering Numbers”. Practice moving beads to the left and watch the numbers change below. Complete moving each row of beads before moving beads in the next row. Try different combination of beads.

Click “Completing the Ten”. Move 5 to 9 beads on the first row. Then move 2 to 9 beads on the second row. An addition statement appears below. Click “COMPLETE”. The beads move to complete the ten. The addition statement that appears shows how the beads have been grouped into tens.

Click “Two Fives”. Move 5 to 9 beads on the first row. Then move 5 to 9 beads on the second row. A addition statement appears. Click “SPLIT”. The beads move to show groups of 5. The addition statement that appears shows how the beads have been grouped into fives.