Subtract within 100: Level 1

The  exercise appears under the Early Math Math Mission. This exercise assists understanding subtraction as taking away groups of ones and tens from each other.

Types of Problems
There are two types of problems in this exercise:


 * 1) Take the tens away This problem has a subtraction problem that involves taking away a multiple of ten from a two-digit number. The student is expected to fill in the blanks with the correct answers to arrive at the difference.Sw100l1-1.png
 * 2) Take the ones away: This problem has a subtraction problem that involves taking away some ones from a two-digit number. The student is expected to fill in the blanks with the correct answer to arrive at the difference.Sw100l1-2.png

Strategies
Knowledge of subtraction as "take-away" is sufficient to complete this exercise.
 * 1) This exercise helps to understand the concept of subtraction via placeholders.
 * 2) In the first problem the first blank is the first digit of the first number in the difference. The second blank is one less than that number. The third blank is the number found in second blank followed by the initial units digit.
 * 3) In the second problem the first blank is the units digit of the first number in the difference. The second blank is one less that that number. The third blank is the first digit of the first number followed by the answer in the second blank.

Real-life applications

 * 1) Understanding the place value at this stage will assist with borrowing with subtraction in the more advanced grades.
 * 2) Subtraction is used to represent the idea of taking away in any context, for example, when buying objects in a store.