The average temperature for Monday, Tuesday, Wednesday and Thursday was 48 degrees, and the average temperature for Tuesday, Wednesday, Thursday and Friday was 46 degrees. If the temperature on Monday was 42 degrees, what was the temperature on Friday?

Introduction / Context:
This question uses overlapping averages over consecutive days. By converting each average into a total for four days and using the known temperature for Monday, we can deduce the temperature for Friday.

Given Data / Assumptions:
- Average temperature for Monday to Thursday = 48 degrees. - Average temperature for Tuesday to Friday = 46 degrees. - Temperature on Monday = 42 degrees. - Temperatures are measured in the same consistent unit (degrees).

Concept / Approach:
Average of four days equals the sum of those four daily temperatures divided by 4. We first find the total temperature for Monday through Thursday, then subtract the Monday temperature to get the sum for Tuesday through Thursday. We also find the total for Tuesday through Friday. Equating the Tuesday to Thursday part from both expressions allows us to solve for the unknown Friday temperature.

Step-by-Step Solution:
Step 1: Let M, T, W, Th and F be the temperatures from Monday to Friday. Step 2: (M + T + W + Th) / 4 = 48, so M + T + W + Th = 192. Step 3: (T + W + Th + F) / 4 = 46, so T + W + Th + F = 184. Step 4: Given M = 42. Step 5: From Step 2, T + W + Th = 192 - M = 192 - 42 = 150. Step 6: Substitute into Step 3: 150 + F = 184. Step 7: Therefore F = 184 - 150 = 34 degrees.

Verification / Alternative check:
Check consistency with averages. If Monday is 42 and the total Monday to Thursday is 192, then the average is 192 / 4 = 48, as stated. For Tuesday to Friday, the total is 150 + 34 = 184 and the average is 184 / 4 = 46, also matching. So the solution is correct.

Why Other Options Are Wrong:
- Values 36, 38, 40 and 42 would change the total for Tuesday to Friday and would not give an average of 46. - Only 34 satisfies both overlapping average conditions at the same time.

Common Pitfalls:
Some learners try to average 48 and 46 or guess a middle value for Friday. Others forget that Monday appears only in the first average and Friday only in the second. Writing equations for sums makes the relationship clear and avoids such confusion.

Final Answer:
The temperature on Friday was 34 degrees.