The total area is a triangle with base 4 and height 2c, so 4c=1 and c=1/4. Then P(X<1.5)=∫01.5x/4dx=9/32. Also P(X<3)=1−∫34(4−x)/4dx=7/8. The conditional probability is (9/32)/(7/8)=9/28≈0.321.
Uses total area to obtain c=1/4.
[1 mark]
Determines P(X<1.5)=9/32.
[1 mark]
Determines P(X<3)=7/8.
[1 mark]
Forms the conditional probability ratio.
[1 mark]
Obtains 9/28≈0.321.
[1 mark]
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.