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Learn different methods to solve subtraction problems easily by jumping on number lines, using a hundreds chart, and applying decomposition, branching, and partial differences rules for accuracy.
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77-22= __ Subtraction Counting Down • Draw the number line • Write the larger number on the right • Decide how many tens and ones to jump down by looking at the smaller number in the equation. Decompose it. • Jump down by tens, then jump down by ones. • (Or another combination jumps that works for you.) • Make sure your jumps add up to the smaller number in the original equation. • *For Accuracy: Check by writing a related addition fact and branching or decomposing to see if you get the big number in the subtraction equation. - 1 - 1 -10 - 10 = 22 (this is the amount subtracted) 55 56 57 67 77
77-22= __ Subtraction Counting Up • Draw the number line • Write the smaller number on the left • Write the larger number on the right • Jump up by tens until you are close to the large number • Jump to the final number by ones or other combinations. • Add up all the jumps to find the difference *For Accuracy: Check by writing a related addition fact and branching or decomposing to see if you get the big number in the subtraction equation. +10 +10 +10 +10 +10 +5 22 32 42 52 62 72 77 10+10+10+10+1+7= 55
Using a Hundreds Chart 77-22=___ When the smaller number is decomposed the values are 20 and 2. • Jump down two rows of 10. • Move backwards 2 ones. • The difference is the number they land on. • When using a hundreds chart the student needs to begin at the number that is the greatest. • Then they can go down in value by tens- rows. • Finally go backwards by ones until the difference is reached- spaces.
Partial DifferencesRule: This method is best used when the ones place in the larger numberis larger in value than the ones place in the smaller number in the equation. 77 – 22 70 7 -20 -2 50 5 50+5=55
DecomposingRule: This method is best used when the ones place in the larger numberis larger in value than the ones place in the smaller number in the equation. 77 – 22 70 + 7 20 + 2 50 + 5 = 55
BranchingRule: This method is best used when the ones place in the larger numberis larger in value than the ones place in the smaller number in the equation. 77 – 22 50 + 5 = 55