A student scores 80, 90, and 70 in three subjects. What score does he need in the fourth subject to achieve an average of 85?

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Q: A student scores 80, 90, and 70 in three subjects. What score does he need in the fourth subject to achieve an average of 85?

Solution: Total score needed for average of 85 = 4 * 85 = 340. Current total = 80 + 90 + 70 = 240. Score needed = 340 - 240 = 100.

Steps: 8

Step 1: Understand that to find the average score, you need to add all the scores together and then divide by the number of subjects.
Step 2: The student has scores in three subjects: 80, 90, and 70.
Step 3: Calculate the total score needed for an average of 85 over four subjects. This is done by multiplying 85 by 4 (the number of subjects).
Step 4: Calculate 85 * 4, which equals 340. This is the total score needed.
Step 5: Now, add the scores the student already has: 80 + 90 + 70.
Step 6: Calculate 80 + 90 + 70, which equals 240. This is the current total score.
Step 7: To find out what score is needed in the fourth subject, subtract the current total score from the total score needed.
Step 8: Calculate 340 - 240, which equals 100. This is the score needed in the fourth subject.