How much do you need to add 243 to make it divisible by10?

Well, honey, if you want to make 243 divisible by 10, you need to add 7 to it. Why 7, you ask? Because 243 + 7 = 250, and 250 is divisible by 10. So, go ahead and sprinkle that 7 on top like the cherry on a sundae.