Addition
Sum of two positive numbers is a positive number.
Example : (+4) + (+2)= +7
Sum of two negative numbers is a negative number.
Example: (-4) + (-5) = -9
Sum of a positive and a negative number is the difference between their magnitudes and give the sign of the number with greater magnitude.
Example: (-5) + (+7) = 2
Subtraction
Subtraction of two numbers is same as the sum of a positive and a negative number.
Example: (+10) – (+3) = 7
Multiplication
a). Product of two positive numbers is positive.
b). Product of two negative number is positive.
c). Product of a positive number and a negative number is negative.
d). Product of more than two numbers is positive or negative depending upon the presence of negative quantities.
If the number of negative numbers is even, then product is positive and if the number of negative numbers is odd then product is negative.
Examples:
(-4) * (+2) = -8
(-3) * (-5) = +15
Division
If both the dividend and the divisor are of same sign, the quotient is always positive.
If the dividend and the divisor are of different sign, the quotient is negative,
Example: (-48) / (+6) = -8
( - 64) / (-8) = +8
What will come in place of question mark ‘?’ in the following question?
45% of 620 - 32% of 560 + ? = 100
a) 0.20 b) 0.30 c) 0.40 d) 0.50
Solution:
Follow BODMAS rule to solve this question, as per the order given below.
Step - 1 - steps of an equation enclosed in ‘Brackets’ must be solved first.
Step - 2 - any mathematical ‘Of’ or ‘Exponent’ must be solved next.
Step - 3 - Next, the parts of the equation that contain ‘Division’ and ‘Multiplication’ are calculated.
Step - 4 - Last but not least, the parts of the equation that contain ‘Addition’ and ‘Subtraction’ should be calculated.
Given Expression,
⇒ 45% of 620 - 32% of 560 + ? = 100
⇒ 0.45 × 620 - 0.32 × 560 + ? = 100
⇒ 279 – 179.20 + ? = 100
⇒ ? = 100 – 99.80 = 0.20
∴ ? = 0.20
Answer: a
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