Which of the following combinations cannot be the side lengths of a triangle? 1. 2.3 inches, 3.4 inches, and 3.2 inches
2. 4.8 inches, 5 inches, and 1.2 inches
3. 2.5 inches, 2.5 inches, and 2.5 inches
4. 6.7 inches, 1.1 inches, and 7.9 inches

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 4.  6.7 inches, 1.1 inches, and 7.9 inches

Step-by-step explanation:

In order for three lengths to be able to form a triangle, the sum of the shorter two must exceed the longest.

1. 2.3 +3.2 > 3.4 . . . will form a triangle

2. 1.2 +4.8 > 5 . . . will form a triangle

3. 2.5 +2.5 > 2.5 . . . will form an equilateral triangle

4. 1.1 +6.7 = 7.8 ≯ 7.9 . . . will not form a triangle

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The symbol ≯ is "not greater than". The typeset version looks like ...

in problems involving proportions, we can use cross products to test whether two ratios are equal and form a proportion. to find the cross products of a proportion, we multiply the outer terms, called the extremes, and the middle terms, called the means.

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