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.

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

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

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


    pingbacks / trackbacks

    Leave a Comment

    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