Create an assignment for your children or class students that illustrates the function of rounding and gives them an opportunity to learn the value of rounding numbers to the appropriate number of significant figures, such as to the nearest tenth and nearest millionth.
Tell your students to imagine that they have a set of numbers that need to be rounded to the nearest integer or nearest whole number. Teach them that if the first digit to the right of the decimal point is smaller than 5, they should drop all digits to the right of the decimal point and leave the first digit to the left of the decimal point unchanged. Illustrate this principle with an example such as: 125.4, 125.3, 125.2 and 125.1 are all rounded to 125.
Teach your students that if the first digit to the right of the decimal point is larger than 5, they should drop all digits to the right of the decimal point and add 1 to the first digit to the let of the decimal point. Illustrate this principle with an example such as: 125.6, 125.7, 125.8 and 125.9 are all rounded to 126.
Teach them that if the first digit to the right of the decimal point is 5 or less and the digit to the left is an even number, they should drop all digits right of the decimal point and leave the first digit to the left of the decimal point unchanged. Illustrate this principle with an example such as: 124.5 is rounded to 124; 122.2 is rounded to 122 and 128.4 is rounded to 128.
Teach your students that if the first digit to the right of the decimal point is 5 and the digit to its left is an odd number that they should drop all digits to the right of the decimal point and add 1 to the first digit to the left of the decimal point. Illustrate this principle with an example such as: 125.5 is rounded up to 126 and 127.5 is rounded up to 128. Teaching students these rounding rules will help them prevent errors when rounding numbers in math problems.
Teach students additional general rules regarding rounding whole numbers such as making numbers that end in 1 through 4 into the next lower number than ends in zero whereas numbers that end in a digit of 5 or more should be rounded up to the next even ten. Illustrate this principle with examples such as: 64 would be rounded down to 60 while 78 would be rounded up to 80. Additionally, teach students the principle that when dealing with large numbers, rounding to the nearest hundred can also help compute figures more easily in one's head without the aid of a calculator. Tell them to round numbers that end in 1 through 49 down to the next lower number that ends in 00. For example, 324 would be rounded to 300. Numbers that have the last digits of 50 or more would be rounded up to the next even hundred. For example, 888 would be rounded up to 900.