Round number minus a number
1.1. Knowledge to remember
1.2. Math forms
Form 1: Calculate
– Set alignment.
– Perform subtraction in turn from right to left, when the unit row of the number being subtracted is not enough to subtract, you need to perform the subtraction with memory.
Form 2: Find x
To find the unknown term, subtract the known term from the sum.
Form 3: Math Quiz
– Read and analyze the topic
– Find the solution of the problem: Pay attention to the keywords “all”; “remaining”… to use appropriate math in solving problems.
– Presentation of the problem.
– Check the solution and the results you just found.
1.3. Solving Textbook Exercises
Perform subtraction of numbers from right to left.
a) x+9=30 b) 5+x=20
To find a term we subtract the other term from the sum.
There are 2 dozen counting sticks, 5 less counting sticks. Ask how much rest tallies ?
– To find the number of remaining sticks, we subtract the number of counting sticks we have initially subtracted from the number of counting sticks.
Change: 2 tens = 20
The number of sticks remaining is:
20 – 5 = 15 (counting stick)
Answer: 15 counting sticks.