Question

Find the value of 405 x 408 using a suitable identity please give a step by step answer

Answer 1

Answer:

165240

Step-by-step explanation:

1) (400 + 5) (400 + 8)

2) Using (x + a) (x + b) = x² + (a + b)x + ab Identity.

3) (400)² + (5 + 8)400 + (5 × 8) = 160000 + 5200 + 40.

4) 165240.

Answer 2

Answer:

$405 \times 408 \\ = (400 + 5)(400 + 8) \\ = {(400)}^{2} + 400(5 + 8) + (5 \times 8) \\ = 160000 + 400 \times 13 + 40 \\ = 160000 + 5200 + 40 \\ = 165240$

405×,408 falls in (x+a)(x+b) formula

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