Question

Find the largest 5 digit no that idms divisible by 7,10,15,21and 28

Answer 1

7 is a prime number, meaning its only divisible by 1 and itself

10 = 2*5 

15 = 3*5

21 = 3*7

28 = 2²*7

2² × 3 × 5 × 7 = 420

So the number should be divisible by 420

Largest five digit number = 99999

99999 ÷ 420 = 238

So remainder is 39.

The largest number divisible = 99999 - 39 = 99960

Answer 2

Answer:

LCM of 7,10,15,21, and 28 by prime factorization method

7 = 1x7

10 = 2x5

15 = 3x5

21 = 3x7

28 = 2x2x7

LCM = 2x2x3x5x7 = 420

The number should be divisible by 420

Now, the largest five-digit number = 99999

99999 = 420 x 238 + 39

Hence the largest number divisible = 99999 - 39

= 99960.

Step-by-step explanation:

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