To make 427398427398427398 divisible by 151515, we need it divisible by both 333 and 555.

Step 1: Check divisibility by 5

A number is divisible by 555 if its last digit is 000 or 555.

  • The last digit of 427398427398427398 is 888.
  • To change 888 into 555, we must subtract 3.

So, consider:

427398−3=427395427398-3=427395427398−3=427395

Now the last digit is 555, so 427395427395427395 is divisible by 555.

Step 2: Check divisibility by 3

A number is divisible by 333 if the sum of its digits is divisible by 333. Digits of 427395427395427395: 4+2+7+3+9+54+2+7+3+9+54+2+7+3+9+5

4+2+7+3+9+5=304+2+7+3+9+5=304+2+7+3+9+5=30

  • 303030 is divisible by 333, so 427395427395427395 is divisible by 333.

Since 427395427395427395 is divisible by both 333 and 555, it is divisible by 151515.

Final Answer

The least number that must be subtracted from 427398427398427398 so that the remaining number is divisible by 151515 is:

3\boxed{3}3​

Mini “Quick Scoop” recap

  • We want: “What least number must be subtracted from 427398 so that the remaining number is divisible by 15?”
  • Make it end in 000 or 555: subtract 333 → 427395427395427395.
  • Check sum of digits: 4+2+7+3+9+5=304+2+7+3+9+5=304+2+7+3+9+5=30, which is divisible by 333.
  • So 427395427395427395 is divisible by 151515, and 3 is the smallest number that works.

TL;DR: Subtract 3 from 427398427398427398 to get a number divisible by 151515.