standard_description: Add and subtract fractions with unlike denominators (including mixed numbers) by replacing given fractions with equivalent fractions in such a way as to produce an equivalent sum or difference of fractions with like denominators. For example, 2/3 + 5/4 = 8/12 + 15/12 = 23/12. (In general, a/b + c/d = (ad + bc)/bd.)
problem_activity: Problem 1
Sondra says
$$3\times223=696$$
. Use what you know about the product of two odd numbers to explain why Sondra is wrong.
Problem 2
Explain two ways you could find the next number in the highlighted diagonal below. You don’t need to actually compute it!
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