Final answer:
The new average when the seventh number, 51, is added to six numbers with an original average of 72, is calculated by summing all seven numbers and then dividing by seven. This results in a new average of 69, which is not one of the provided options.
Step-by-step explanation:
The question asks us to calculate the new average when a seventh number is added to an existing set of six numbers that have an average of 72.
If the average of six numbers is 72, the total sum of these numbers is 6 × 72 = 432.
When the seventh number, which is 51, is added, the new sum becomes 432 + 51 = 483.
To find the new average, we divide the total sum by the number of values, which is now seven.
So, the new average would be 483 ÷ 7 = 69.
This means that the new average is slightly lower than the original average of 72.
Thus, the correct answer, which is not listed in the options provided, is that the new average is 69.