​If a = 4011 and b = 3989, then value of ab = ​

Correct option is A

Solution

We need to calculate the value of a $$\times$$​ b , where a = 4011 and b = 3989 .

Step-by-Step Solution:

1. Given:

a = 4011,  b = 3989

2. Use the Difference of Squares Formula:

The numbers 4011 and 3989 are close to their midpoint 4000 .

Let:

a = 4000 + 11, b = 4000 - 11

Then:

​$$a \times b = (4000 + 11)(4000 - 11)$$​

3. Apply the Formula:

Using (x + y)(x - y) = $$x^2 - y^2$$​ , where x = 4000 and y = 11 :

​$$a \times b = 4000^2 - 11^2$$​

4. Calculate Each Term:

$$4000^2 = 16,000,000$$​

$$11^2 = 121$$​

​$$a \times b = 16,000,000 - 121 = 15,999,879$$​

Final Answer:

​$$\boxed{15,999,879}$$​