Similar Triangles: Calculate the Ratio Between ABC (12,9,6) and KLT (4,3,2)

SSS Similarity Criterion with Ratio Calculations

Are the triangles below similar? If so, what is their ratio?AAABBBCCCKKKLLLTTT6912342

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Step-by-step video solution

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00:00 Are the triangles similar?
00:03 Let's find the ratio of corresponding sides
00:09 If the ratio of all sides is equal, then the triangles are similar
00:13 Let's substitute appropriate values according to the given data and find the similarity ratio
00:29 The ratio of all sides is equal, therefore the triangles are similar
00:34 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

Are the triangles below similar? If so, what is their ratio?AAABBBCCCKKKLLLTTT6912342

2

Step-by-step solution

To determine if the triangles ABC \triangle ABC and KLT \triangle KLT are similar, we apply the Side-Side-Side (SSS) similarity criterion. This requires that the ratios of corresponding sides are equal.

We are given the side lengths: BC=12 BC = 12 , AB=9 AB = 9 , CA=6 CA = 6 for ABC \triangle ABC , and LK=2 LK = 2 , KT=3 KT = 3 , LT=4 LT = 4 for KLT \triangle KLT .

First, find the ratio for each pair of corresponding sides:

  • Compare BC BC and LT LT : BCLT=124=3 \frac{BC}{LT} = \frac{12}{4} = 3
  • Compare CA CA and LK LK : CALK=62=3 \frac{CA}{LK} = \frac{6}{2} = 3
  • Compare AB AB and KT KT : ABKT=93=3 \frac{AB}{KT} = \frac{9}{3} = 3

Since BCLT=CALK=ABKT=3 \frac{BC}{LT} = \frac{CA}{LK} = \frac{AB}{KT} = 3 , all sides maintain a constant ratio. Hence, the triangles are similar.

The similarity ratio is 3 3 , indicating ABCKLT \triangle ABC \sim \triangle KLT with a ratio of 3:1.

The correct choice, as given in the options, is:

Yes, similarity ratio:
BCLT=CALK=ABKT \frac{BC}{LT}=\frac{CA}{LK}=\frac{AB}{KT}

3

Final Answer

Yes, similarity ratio:
BCLT=CALK=ABKT \frac{BC}{LT}=\frac{CA}{LK}=\frac{AB}{KT}

Key Points to Remember

Essential concepts to master this topic
  • SSS Similarity Rule: All three pairs of corresponding sides must have equal ratios
  • Technique: Calculate each ratio: 124=62=93=3 \frac{12}{4} = \frac{6}{2} = \frac{9}{3} = 3
  • Check: All ratios equal 3, so triangles are similar with scale factor 3:1 ✓

Common Mistakes

Avoid these frequent errors
  • Comparing sides in wrong order
    Don't match sides randomly like BC with LK = 12/2 = 6 and AB with LT = 9/4 = 2.25! These unequal ratios suggest no similarity when triangles actually are similar. Always identify corresponding sides carefully by comparing side lengths in order.

Practice Quiz

Test your knowledge with interactive questions

Is the similarity ratio between the three triangles equal to one?

FAQ

Everything you need to know about this question

How do I know which sides correspond to each other?

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Look at the side lengths and match them by size! The longest side of one triangle corresponds to the longest side of the other. Here: BC=12 (longest) matches LT=4 (longest), CA=6 (shortest) matches LK=2 (shortest).

What if I get different ratios for each pair of sides?

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If the ratios are different, then the triangles are not similar! For similarity, all three ratios must be exactly equal. Even small differences mean the triangles don't have the same shape.

Does the order of the ratio matter?

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Yes! Always write the ratio as larger triangle : smaller triangle consistently. Here we use ABCKLT \frac{ABC}{KLT} giving ratios of 3, not KLTABC \frac{KLT}{ABC} which would give ratios of 1/3.

Why is the similarity ratio 3:1 and not just 3?

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The ratio 3:1 shows the relationship clearly - triangle ABC is 3 times larger than triangle KLT. We can also write it as just "3" or as the fraction 31 \frac{3}{1} .

Can I use this method for any triangle similarity problem?

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SSS similarity works when you know all three side lengths of both triangles. If you only know some sides or angles, you'll need different methods like SAS or AA similarity.

What happens if triangles are similar but oriented differently?

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Orientation doesn't matter! Similar triangles can be rotated, flipped, or positioned differently and still be similar. Focus on matching corresponding sides by length, not by position in the diagram.

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