To solve for the original number when decreased by 20% becomes 136, we can follow these steps:
1. Understand the Problem:
- Decreasing a number by 20% means the number is multiplied by [tex]\( 0.8 \)[/tex] (since 100% - 20% = 80%, and 80% as a decimal is 0.8).
- We are given that this decreased value is 136.
2. Set Up the Equation:
- Let [tex]\( x \)[/tex] be the original number.
- According to the problem, when [tex]\( x \)[/tex] is decreased by 20%, the new value is [tex]\( 0.8x \)[/tex].
- We know [tex]\( 0.8x = 136 \)[/tex].
3. Solve for [tex]\( x \)[/tex]:
- To find [tex]\( x \)[/tex], we need to isolate it on one side of the equation.
- Divide both sides of the equation by 0.8.
[tex]\[ x = \frac{136}{0.8} \][/tex]
4. Calculate the Value of [tex]\( x \)[/tex]:
- Performing the division,
[tex]\[ x = 170 \][/tex]
So, the original number is [tex]\( 170 \)[/tex].
Therefore, the correct answer is (c) 170.
