Divisibility Shortcuts

Divisibility rules tell you instantly whether a division comes out clean:

• Ends in an even digit → divides by 2
• Digits sum to a multiple of 3 → divides by 3
• Ends in 0 or 5 → divides by 5
• Digits sum to a multiple of 9 → divides by 9

Ask whether 738 divides by 3: add 7 + 3 + 8 = 18, a multiple of 3, so yes — no division needed. The rule for 7 is trickier: double the last digit, subtract it from the rest, and check if the result divides by 7.