KEY CONCEPTS in Maths

NOTE
(A) 
★ You can add numbers in any order. Answer remains the same.
21 +78 = 78 + 21

★ Zero added to any number gives the same number as the sum.
94 + 0 = 94

★ One added to any number gives its successor as the sum.
94 + 1 = 95

(B) 
Zero subtracted from any number gives the same number as the difference. 
12 – 0 = 12

★ Any number subtracted from itself will give zero as the difference.
12 – 12 = 0

★ One subtracted from any number gives its predecessor as the difference.
OR
★ One subtracted to any number gives its predecessor.
94 – 1 = 93

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Go EASY!

Keywords for addition:
★ How much is the amount in all
★ Find the total or sum
★ Increased by
★ Together
★ Added to
★ More than 

Keywords for subtraction:
★ How many did not have
★ How much more
★ How many more
★ Decreased by
★ Difference
★ Fewer
★ Remain
★ Less than
★ Take away
★ Have left
★ Taller/Shorter
★ Change

We multiply

★ when quantity of something is increased many times.
★ when the value of 1 item is given and we have to find out the value of more items. c. when we have to find out the product of two or more numbers.

We divide

★ when something is distributed or shared equally.
★ when we know the value of many quantities and we have to find out the value of one quantity.

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Multiplication by 15 
We can split the number 15 as (10+5). 
To multiply a number by 15, we first multiply the number by 10. Then halve the product obtained and add the same to the first product.

Example 7: Multiply: 178 x 15 Solution:
178 x (10+5)=(178 x 10) + (178 × 5)
= 1780 + 890=2670
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DIVISION

Division means dividing or sharing something in equal parts. 

Dividend: The number that has to be divided. Denote it as capital D

Divisor: The number that divides the dividend. 
Denote it as small d

Quotient: The result of dividing a dividend by a divisor. 
Denote it as capital Q

Remainder: The number left after division and its value is less than the divisor: 
Denote it as capital R

To verify the result of division, we use the following: 
Dividend = (Divisor x Quotient) + Remainder

Verification
D = d × Q + R 

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