# Hundreds Board

A hundreds board is a 10x10 board with cells displaying the numbers 1-100. Some hundred boards display the numbers 0-99 instead, and some include more than 100 numbers. Hundreds boards are powerful manipulatives for students to visualize the base-ten structure of our number system because each number is one more(less) than the number to its left(right), and ten more(less) than any number above(below) it.

Virtual Hundreds Board Manipulative

Virtual manipulatives, such as Brainingcamp's Fraction Manipulatives, include features that are difficult or impossible to do with physical manipulatives. Single numbers can be highlighted with a simple tap, and multiple numbers can be selected with an easy swipe. All multiples can be automatically highlighted, making it easy to explore multiples and least common multiples. A "rounding" mode uses a tilted hundreds board so that users can place a ring on a number and see that ring slide to its rounded value. A specialized mode models addition by showing that the ones place of the second operator indicate how many places to move horizontally and the tens place of the second operator indicate how many places to move vertically.

Using a Hundreds Board

When adding two-digit numbers, the tens place of the second operand determines the number of places to move up/down from the first operand and the ones place of the second operand determines the number of places to move left/right from the first operand. To add 34 + 35, start with the numbers 34 and then move down 3 places and right 5 places. The resulting location holds the number 69, so 34 + 35 = 39.

Identifying Numbers

If you have (or can make) a set of individual 1-100 number tiles, cover the numbers on the board, randomly draw tiles, and them place them at their correct location on the hundreds board. See how fast you can complete the board.

Multiples

To find all the multiples of a number, skip count by that number. To find common multiples for two numbers, find multiples for both numbers and note which multiples are common to both. The least common multiple is the smallest number that is a multiple of both.

Place Value

Notice that each increase(decrease) in the Ones value corresponds to an increase(decrease) horizontally on the hundred board. Each increase(decrease) in the Tens value corresponds to an increase(decrease) vertically on the hundred board. Pick a number and confirm that moving 10 places horizontally is the same as moving 1 place vertically.

Prime Numbers

The following activity will highlight all the non-prime numbers on a hundreds board, leaving all the prime numbers without highlights. Highlight the number 1 because it is non-prime (prime numbers are greater than 1). The next non-highlighted number is 2. Don't highlight the number 2 but highlight all its multiples (all even numbers). The next non-highlighted number is 3. Donâ€™t color the number 3, but color all its multiples. Continue on. It turns out that by the time the multiples of 7 have been highlighted, all non-highlighted tiles are prime numbers.

Rounding

A hundreds board is a great tool for visualizing how numbers round up or down to the nearest 10. Draw a line between the columns ending in 4 and 5. Numbers to the left of the line round down to the nearest ten, and any number to the right of the line round up to the nearest ten. The Brainingcamp Hundreds Board manipulative has a special Rounding mode where users can drop a ring on a kinked hundreds board and see the ring roll to the number it rounds to.

Skip Counting

Skip count numbers by highlighting numbers as you go. Look for visual patterns.

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