Answer:
11/64
Step-by-step explanation:
Each question can be answered in 2 ways
∴ Total ways in which 10 questions can be answered
=2¹⁰
No. of ways of guessing at least 7 questions
out of 10
=7 questions correct +8 questions correct
+9 questions correct +10 questions correct
= ¹⁰C7(1)⁷+ ¹⁰C8(1)⁸+ ¹⁰C9(1)⁹+ ¹⁰C10(1)¹⁰
= 120 + 45 + 10 +1
=176
..Required Probability =176/2¹⁰
.. =11×16/2¹⁰
=11/64
