Question

If 3+3=21 ,5+5=195, 7+7=609 ,then 9+9=?

Answer 1

Answer:

1359

Step-by-step explanation:

3^3 + 3^3 = 27 + 27 = 54

                = 54 - 33 = 21

5^3 + 5^3 = 125 +125 = 250

                = 250 - 55 = 195

7^3 + 7^3 = 343 + 343 = 686

                = 686 - 77 = 609

9^3 + 9^3 = 789 + 789 = 1458

                = 1458 - 99 = 1359

Answer 2

Given:

3+3=21

5+5=195

7+7=609

To find:

9+9=?

Solution:

In the given series first, we cube the equation then add the value after add subtract from the given value it will give the correct answer:

Formula:

$\bold{(a^3+b^3)-ab} \ where \ ab \ is \neq a \times b$

solve:

$\to (3^3+3^3)-33\\\\\to (27+27)-33\\\\\to (54)-33\\\\\to 54-33\\\\\to 21$

Similarly:

$\to (9^3+9^3)-99\\\\\to (729+729)-99\\\\\to (1458)-99\\\\\to (1458-99)\\\\\to 1359$

The final answer is "1359".