How do I estimate the area under a graph?

• To find an estimate for the area:
  • Split area into vertical strips
  • Draw straight lines at top of strips
  • Find area of strips (trapeziums) using Area = ½(a + b)h
  • Add the areas

How do I know if my answer is an underestimate or an overestimate?

• A common exam question is to ask if your estimate of the area is an underestimate or an overestimate
• To answer this, simply look at the straight lines joining the tops of your strips
  • If the straight lines are below the curve, it is an underestimate
  • If the straight lines are above the curve, it is an overestimate
• At GCSE, the lines will all be below or all be above the curve- though it may be difficult to tell which for some strips