FREQUENTLY MADE MISTAKES TOPIC WHOLE NUMBERS
1. Confusion about place value and digit value
Example : State the digit value of 9 in the number 89 143
The digit value of 9 in the number 89 143 is thousands. (wrong)
The digit value of 9 in the number 89 143 is 9 000 (correct)
2. When performing addition, subtraction, multiplication or division in the vertical
form, the numbers must be arranged according to the place value.
Example : 19 850 + 4 678
19 850 1 9 8 5 0
+ 46 78 (wrong) + 4 6 7 8 (correct)
66 630 2 4 5 2 8
3. When performing mixed operations with whole numbers, calculation must be
carried out acording to the general principles.
Example : 4 980 + 1 137 x 60
4 980 + 1 137 x 60 (wrong) 4 980 + 1 137 x 60 (correct)
= 6 117 x 60 = 4 980 + 68 220
= 367 020 = 73 200
FREQUENTLY MADE MISTAKES (FRACTIONS)
1. When converting mixed numbers to improper fractions.
Example : Convert 4 1 to an improper fraction.
7
4 x 7 = 28 (wrong) ( 4 x 7 ) + 1 = 29 (correct)
7 7 7 7
2. When adding and subtract fractions
Example : 1/9 + 5/9 = 6/18 (wrong) 1/9 + 5/9 = 6/9 (correct)
3. When using cancellation method
Example :
1/4 + 4/5 = 1 + 1/5
1/4 + 4/5 = 1 + 1/5
= 1 1/5 (wrong)
1/4 + 4/5 = 5/20+16/20
= 21/20
= 1 1/20 (correct)
FREQUENTLY MADE MISTAKES (DECIMALS)
1. When adding and subtracting decimals,decimal points must be aligned in a straight line.
Example : 289 . 14 + 15 . 3 =
2 8 9 .1 4 2 8 9 . 1 4
+ 1 5 .3 + 1 5 . 3
2 9 0 6 . 7 (wrong) 3 0 4 . 4 4 (correct)
2. When multiply and divide decimals,decimal point must be aligned in straight line.
Example : 6 8 5 x 0.7
6 8 5 6 8 5
x 0 . 7 x 0. 7
4 7 9 5 (wrong) 4 7 9 . 5 (correct)
