Five good light bulbs and two defective ones were mixed up unknowingly. To identify the defective ones for disposal, the bulbs are tested one one by one. (a) If both defective ones are identified in the testing of the second one, what is the probability of such a ‘lucky’ break? (b) If three bulbs had to be tested to get the two defective ones, what is the probability of such an event.

2

Explanation:

The scale factor is the ratio between the scale drawing measures and the actual measures.

                                   scale drawing length            8 inches
scale factor = ratio = =   = 2
                                        actual length                    4 inches

Also,
                                   scale drawing width             14 inches
scale factor = ratio = =       = 2
                                         actual width                      7 inces

As seen the scale factor is 2.