Question

Find greatest 4 digit number which is exactly divisible by 20 28 45
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Answer 1

Answer:

The greatest 4 digit number which is exactly divisible by 20 28 45 is the LCM of 20, 28 and 45.

_______________  

       2  | 20, 28, 45

           |_______________

       2  |  10, 14, 45  

           |_______________

      3   |   5, 7, 45

           |_______________

       3  |   5, 7, 15  

           |_______________

       5  |   5, 7, 5

           |_______________

       7  |   1, 7, 1

           |_______________

           |   1, 1,  1

Thus, LCM= 2*2*3*3*5*7=1260.

Now, we will divide the greatest 4 digit number by 360.

The greatest 4 digit number is 9999.

            ______

  1260 ) 9999 (7

             8820

             _____

              1179   - Remainder.

            ------------

Now, we have to subtract the remainder, which is 1179, from 9999.

⇒ 9999 - 1179 =  8820

So, 8820 is the required greatest 4 digit number which is exactly divisible by 20, 28, 45.

HOPE THIS HELPS :D