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In a class of 50 students, every student must offer at least one subject. 40 students offered physics and 30 offered biology. How many offered both physics and biology?

• A. 70
• B. 20
• C. 42
• D. 54

QUICK ANSWER…

B

SOLUTION…  

If the number of students that offered both is x,

Then the number that offered physics alone = 40 – x

And the number that offered biology alone = 30 – x

Solving for x, we have:

(40 – x) + (x) + (30 – x) = 50

40 – x + x + 30 – x = 50

70 – x = 50

70 – 50 = x

20 = x

x = 20

Hence, the number of students that offered both physics and biology is 20.

Now for the right answer to the above question:

1. Option A is incorrect.
2. Option B is correct.
3. C is incorrect.
4. D is not the correct answer.

QUICK TIPS…

You may please note these/this:

• When resolving a problem with Venn diagram, ensure you take care of the middle first, and then subtract this middle from subsequent values as shown above.

Use the questions and answer session to correct, express, and contribute your views.

/culled from 2019 JAMB-UTME mathematics question 5 /