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Page 1 of 1 SKILL: USING GRIDS TO ESTIMATE Chloroplast Math MATH TUTORIAL CLASSZONE.COM Click on Math Tutorial for more help with perimeter and area. You can’t count the number of chloroplasts in a leaf very easily, but you can estimate the number. For example, if you know the number of chloroplasts in a small area, you can estimate the number of chloroplasts in a whole leaf. Example Suppose you are studying how lilacs make food from sunlight. You read that there are 50 million chloroplasts for every square centimeter of a leaf. You want to know the number in a whole leaf. (1) Cover the leaf with centimeter grid paper. (2) Count the number of whole squares covering the leaf. 7 1 cm (3) Match pairs or sets of partly covered squares, that add up to a whole square. 7 5 12 1 cm (4) Add on any remaining 0.5 (half), 0.025 (quarter), or 0.75 (three-quarters) of a square. 12 .5 12.5 (5) Finally, multiply the number of squares by the number of chloroplasts in one square. ANSWER 50,000,000 12.5 625,000,000. Give estimates for the following amounts. 1. Trace the beech leaf shown on this page onto a sheet of centimeter grid paper. What is the leaf’s approximate area in cm2? 2. About how many chloroplasts are in this beech leaf? 3. A eucalyptus leaf is long and thin. Suppose a healthy leaf is 1.5 centimeters wide and 6 centimeters long. Estimate its area. Hint: Make a sketch. 4. What is the approximate number of chloroplasts in the eucalyptus leaf described above? CHALLENGE Collect two leaves. Trace the leaves on centimeter grid paper. Label each tracing with its name, estimated area, and its approximate number of chloroplasts. Chapter 3: Plants 115