Completing a weekly temperature average from six given days: The minimum temperatures from Monday to Saturday are 20°, 18.6°, 17°, 21.4°, 19°, and 19.8°. The weekly average (7 days) is 19.5°. What is Sunday’s minimum temperature?

Introduction / Context:
Given a total weekly average and six daily values, we can deduce the seventh by working with totals: weekly total = average * 7. Subtract the known six-day total to get the missing day.

Given Data / Assumptions:

• Known six days: 20, 18.6, 17, 21.4, 19, 19.8
• Weekly average = 19.5 over 7 days

Concept / Approach:
Sunday = 7 * 19.5 − sum(Mon…Sat). Compute the six-day sum carefully, then subtract from 136.5.

Step-by-Step Solution:
Sum(Mon…Sat) = 20 + 18.6 + 17 + 21.4 + 19 + 19.8 = 115.8Weekly total = 7 * 19.5 = 136.5Sunday = 136.5 − 115.8 = 20.7°

Verification / Alternative check:
Add 20.7 to the six-day sum: 115.8 + 20.7 = 136.5; divide by 7 to get 19.5, confirming the average.

Why Other Options Are Wrong:
16.9, 11.6, and 12.6 do not satisfy the weekly average; 21.2 overshoots the required total.

Common Pitfalls:
Arithmetic slips when summing decimals; align decimals and verify with a quick reverse check.

Final Answer:
20.7°