Brackets

Of

Division

Multiplication

Addition

Subtraction

According to BODMAS, Division $(÷),$ is done before Multiplication $(\times ),$ which is followed by Addition $(+)$ & and then by Subtraction $(-)$. 

Only even numbers are divisible by 2. No odd number is divisible by 2. Hence 2002 is the number divisible by 2.

3460 $\times$ 7599

3460 can be rounded off to 3000,

as 3460 < 3500

7599 is rounded off to 8000,

as 7599 > 7500

Hence the estimate is 

3000 $\times$ 8000 

3 $\times$ 8 = 24 followed by 6 zeroes = 2,40,00,000
 

Applying Distributive property of multiplication over addition to simplify: 

$(18\times 50)+(18\times 9)$

=$18\times (50+9)=18\times 59$

216 Increased by 93

$=216\underset{–}{+93}\underset{–}{309}$

309 decreased by 9

$=309\underset{–}{-9}\underset{–}{300}$

Hence "300" is the answer.

When any 2 even numbers are multiplied

eg. $2\times 8=16or12\times 12=144,$ the product is always an even number. 

The numbers between 40 and 50 that are exactly divisible by 7 ( those numbers that can be divided by 7, without leaving a remainder) are 42 and 49.

$42=7\times 6$

$49=7\times 7$

The sum of 42 and 49 is 91

$42\underset{–}{+49}\underset{–}{91}$

Hence "91" is the sum.

The product of 2 whole numbers is 48.

Given below are the pairs of factors of 48 and their sum.

$\begin{array}{cc}1\times 48& 48+1=49\\ 2\times 24& 24+2=26\\ 3\times 16& 16+3=19\\ 4\times 12& 12+4=16\\ 6\times 8& 8+6=14\end{array}$

Hence "6,8" are the possible numbers.

$640+360$ apples make 1000 apples

$640\underset{–}{+360}\underset{–}{1000}$

1000 apples equally divided into 50 boxes  

= $1000÷50=\frac{100\text{/}0}{5\text{/}0}$

$=\frac{100}{5}=20$ apples in each box.

Alternate Method

$1000÷50=20$ apples in each box

21978 when reversed gives 87912. So the units digit of the product must be 2. 

In the original number, the unit digit is 8. To get 2 in the unit digit in the product, 8 must be multiplied with either 4 or 9.

$8\times 4=32$ or $8\times 9=72$

The tens digit in the reversed number 87912 is 1. To get that, we need to multiply by 4.

$2\stackrel{3}{1}\stackrel{3}{9}\stackrel{3}{7}8\times \underset{–}{4}\underset{–}{87912}$

Hence,  21978 is multiplied by '4' to get a product where the digits are exactly reversed.