fast multiplication result?

Question

I need to choose an answer for this multiplicative result .

Rs 2850 Lakhs x 1.06 x 1.06 = ?

1) Rs 29.2 crore

2) Rs 32.02 crore

3) Rs 25.04 crore

4) Rs 34.5 crore


How do i choose the correct answer .

The point is , i want to select answer very fast , quickly consuming minimal amount of time.

Obviously , i am not going to multiply fully .

can you teach me a trcik by which i can choose the answer in a quicker way .

There is a decimal number 1.06 in the multiplication and this is making a big trouble in selecting the answer.


However , i am asking you a technique by which i can select the answer early .

Answer 1

1.06 x 1.06 =
1 + 2 x .06 + .06^2 =
1 + 0.12 + 0.0036
Now decide on the precision you want:
2850 = 1 x 2850
. 285 = .1 x 2850
3135
. . 57 = .02 x 2850
3192
. . 11.4 = 0.004 x 2850
3203.4
. . - 1.14 = - 0.0004 x 2850
3202.26

---all done without using a calculator---

Answer 2

(1.06)*2 is about 1.12 which is about 9/8, 9/8 of 28 is 31.5. subce we started with 2850 instead., about 32.