so, he is using 3 of the 1/5 strips to get a 3/5, 1/5 + 1/5 + 1/5 = 3/5
now, he wants to model the same fraction, but with a different fashion, with a denominator of 10, one-tenth, yet equivalent.
the cheap answer is, multiply top and bottom by 2.
[tex]\bf \cfrac{3}{5}\cdot \cfrac{2}{2}\implies \cfrac{3\cdot 2}{5\cdot 2}\implies \cfrac{6}{10}\qquad thus\\\\
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\cfrac{1}{10}+\cfrac{1}{10}+\cfrac{1}{10}+\cfrac{1}{10}+\cfrac{1}{10}+\cfrac{1}{10}\implies \cfrac{6}{10}\implies \cfrac{3}{5}[/tex]
