Question

lesson 13: charts and graphs
stem and leaf plots
what was the average temperature for the month of april in washington d.c.?
a. 65 degrees
b. 59 degrees
c. 61 degrees
d. 69 degrees
check answer
stem-and-leaf plot titled daily average temperature (°f), washington d.c. (april 2010):
stem 5: leaf 3, 5, 3, 5, 9, 8, 0, 6, 8, 5, 9, 8, 6, 2, 8
stem 6: leaf 0, 5, 1, 6, 9, 1, 4, 2, 3, 5, 6
stem 7: leaf 6, 7, 0, 1
source: national weather service forecast office...

Explanation:

Step1: Count number of data points

For stem 5: Let's count the leaves. The leaves are 3, 5, 3, 5, 9, 8, 0, 6, 8, 5, 9, 8, 6, 2, 8. Let's count them: 15 values.
For stem 6: Leaves are 0, 5, 1, 6, 9, 1, 4, 2, 3, 5, 6. Count: 11 values.
For stem 7: Leaves are 6, 7, 0, 1. Count: 4 values.
Total number of days in April (data points) = 15 + 11 + 4 = 30.

Step2: Calculate sum for stem 5

Stem 5 means the tens place is 5, so each leaf is the ones place. So the temperatures are 53, 55, 53, 55, 59, 58, 50, 56, 58, 55, 59, 58, 56, 52, 58.
Let's sum them:
53 + 55 = 108; 108 + 53 = 161; 161 + 55 = 216; 216 + 59 = 275; 275 + 58 = 333; 333 + 50 = 383; 383 + 56 = 439; 439 + 58 = 497; 497 + 55 = 552; 552 + 59 = 611; 611 + 58 = 669; 669 + 56 = 725; 725 + 52 = 777; 777 + 58 = 835. So sum for stem 5 is 835.

Step3: Calculate sum for stem 6

Stem 6 means tens place 6, so temperatures: 60, 65, 61, 66, 69, 61, 64, 62, 63, 65, 66.
Sum: 60 + 65 = 125; 125 + 61 = 186; 186 + 66 = 252; 252 + 69 = 321; 321 + 61 = 382; 382 + 64 = 446; 446 + 62 = 508; 508 + 63 = 571; 571 + 65 = 636; 636 + 66 = 702. Sum for stem 6 is 702.

Step4: Calculate sum for stem 7

Stem 7 means tens place 7, temperatures: 76, 77, 70, 71.
Sum: 76 + 77 = 153; 153 + 70 = 223; 223 + 71 = 294. Sum for stem 7 is 294.

Step5: Total sum and average

Total sum = 835 + 702 + 294 = 1831.
Average = $\frac{1831}{30} \approx 61$ (since 1831 ÷ 30 ≈ 61.03, which rounds to 61).

Answer:

c. 61 degrees