Chapter 1.1, Problem 39E

To determine

To determine the error in the solution.

Explanation of Solution

Given:

  

Calculation:

  $\Rightarrow -0.8+r=12.6$

  $\Rightarrow -0.8+r+0.8=12.6+0.8$(Adding 0.8 on both sides)

  $\Rightarrow r=13.4$

Comparison:

Now both the correct and incorrect solutions are compared side by side to obtain a conclusion.

(i)(ii)

From looking at both the solutions, it is clear that, in (ii), the second step has an error.

In that solution, instead of adding 0.8, he added -0.8.

Conclusion:

Hence, in the given solution second step has an error.