MATH STRAND VII:
ESTIMATION AND MENTAL COMPUTATION
19. Apply appropriate strategies to find estimates of sums, differences, products, and quotients of whole numbers and determine whether the estimate is greater than or less than the exact result.
Items for this learning outcome may be completed using any of a number of effective estimation strategies. The most commonly used strategies used in estimating sums, differences, products, and quotients include:
a) front-end estimation strategy (uses front-end digits to obtain an initial estimate and may make adjustments to refine estimate.)
b) rounding strategy including flexible rounding (involves rounding numbers, computing with rounded numbers, and sometimes includes an adjustment step. The purpose of the rounding is to produce mentally manageable numbers. Flexibility in method of rounding is needed to fit the particular situation, operation, and numbers involved.)
c) compatible numbers strategy (looks at all numbers involved in the problem and changes or rounds each number so it can be paired usefully with another number. The strategy also involves flexible rounding process to find numbers that easily “fit together” and are easy to manipulate mentally.)
d) clustering strategy (used when a group of numbers cluster around a common value, a reasonable group average determined by selecting a convenient multiple around which all the data cluster and multiplying it by the total number of numbers in the group.)
e) special number strategies (looking for numbers that are near “special numbers” such as powers of ten, common decimals and fractions that are easy to compute mentally and changing the existing problem into a new form that will have an approximately equivalent answer.)
Students may be asked to describe their estimate in relation to the exact result.
20. Estimate the sum, difference, product, or quotient of decimal numbers by rounding, ana the sum, difference, or product of fractions and/or mixed numbers by rounding the fractions to 0, ½, or 1.
Items testing this outcome require the student to round decimal numbers to estimate sums, differences, products, or quotients. Other test items may require the student to round fractions to 0, ½, or 1 to estimate the sum, difference, or product of fractions and/or mixed numbers.
Items focus on extending estimation strategies to situations involving decimals and fractions. Students will be expected to apply strategies using rounding and/or special numbers to make estimates.
Students will be expected to give an estimate when asked and not give the actual computation. Giving the exact answer and not the estimate will be considered incorrect.
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