Question

Jack can solve $80\%$ of the questions of maths while Sam can solve $70\%$ of the questions. What percentage of questions can be solved by them from a maths book.

• A. $89\%$
• B. $91\%$
• C. $93\%$
• D. $94\%$

Answer 1

The correct option is D $94\%$

Assuming that Jack and Sam's abilities to answer particular questions are independent, so

Probability both can solve $=0.8\times 0.7=0.56$

Probability Jack can solve but Sam cannot$=0.8\times 0.3=0.24$
Probability Jack cannot solve but Sam can $=0.2\times 0.7=0.14$
probability neither can solve $=0.2\times 0.3=0.06$

So, total Probability $=0.56+0.24+0.14=0.94$

.

Therefore, Correct Answer is $94\%$