2013 A-level H1 Mathematics (8864) Question 8 Suggested Solutions

All solutions here are SUGGESTED. Mr. Teng will hold no liability for any errors. Comments are entirely personal opinions.

(i)
Let X denote the number of batteries with lifetime of at least 100 hours, out of 10.

X ~\sim~ \mathrm{B}(10, 0.8)
\mathrm{P} (X=10) = 0.107

(ii)
\mathrm{P} (X \ge 10) = 0.678

(iii)
Let Y denote number of packs that satisfy the customer, out of 80.

Y ~\sim~ \mathrm{B}(80, 0.6777995)

Since n = 80 is large, np = 54.224 > 5, nq = 25.776 >5
\Rightarrow Y ~\sim~ \mathrm{N}(54.224, 17.471) approximately

\mathrm{P} (Y \ge 60)
= \mathrm{P} (Y \ge 59.5) by continuity correction

\approx 0.103

KS Comments

Remember to do CONTINUITY CORRECTION!!!

Comments
pingbacks / trackbacks

Leave a Comment

11 + 3 =

Contact Us

CONTACT US We would love to hear from you. Contact us, or simply hit our personal page for more contact information

Not readable? Change text. captcha txt

Start typing and press Enter to search