Estimate a 15% tip on a dinner bell of $49.76 by first round the bill amount to the nearest $10

Estimate a 15% tip on a dinner bell of $49.76 by first round the bill amount to the nearest $10.

Round the bill to the nearest $10

• $49.76 is in between ($40, $50)
• 1/2 of that interval is (40 + 50)/2 = 90/2 = 45
• Since $49.76 is greater than or equal to 45, we round up to $50

Add a 15% tip
50(1 + 0.15) = 50 + 7.50 = $57.50