Raj scored 67, 69, 78 and 88 in 4 of his subjects. What should be his score in the `5^(th)` subject so that his average equals 80 ?
A. 88
B. 90
C. 96
D. 98

Options

A. C
B. D
C. A
D. B

Answer

To find out what Raj should score in his 5th subject so that his average score equals 80, we can follow these steps:

### Step 1: Calculate the sum of the scores in the first four subjects.
Raj scored 67, 69, 78, and 88 in his first four subjects. We need to add these scores together.

\[ \text{Sum} = 67 + 69 + 78 + 88 \]

### Step 2: Perform the addition.
Let's add these numbers step by step:

1. \( 67 + 69 = 136 \)
2. \( 136 + 78 = 214 \)
3. \( 214 + 88 = 302 \)

So, the total score from the first four subjects is 302.

### Step 3: Set up the equation for the average.
The average score is calculated by dividing the total score by the number of subjects. Since Raj wants his average to be 80 after 5 subjects, we can set up the equation:

\[ \text{Average} = \frac{\text{Total Score}}{\text{Number of Subjects}} = 80 \]

Substituting the known values gives us:

\[ \frac{302 + x}{5} = 80 \]

where \( x \) is the score Raj needs in the 5th subject.

### Step 4: Solve for \( x \).
To find \( x \), we first multiply both sides of the equation by 5:

\[ 302 + x = 400 \]

Next, we isolate \( x \) by subtracting 302 from both sides:

\[ x = 400 - 302 \]

Calculating this gives:

\[ x = 98 \]

### Conclusion:
Raj needs to score **98** in his 5th subject to achieve an average of 80.