1) 15/19 * 19/15 = 1
4 87/91 * 1 = 4 87/91
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2) 11/14 * 14/11 = 1
1 1/7 * 1 = 1 1/7
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3) 1 4/5 * 5/9 = 9/5 * 5/9 = 1
3,14 * 1 = 3,14
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4) 3 1/7 * 7/22 = 22/7 * 7/22 = 1
4,8 * 1 = 4,8