In a playground, the ratio of the number of adults to the number of children is
13:6. If
9 adults and
24 children enter the playground, then the ratio of the number of adults to the number of children is
8:7. Find the original number of adults in the playground. (4 marks)
The equation of the straight line
L is
5x−7y−14=0. If
P is a moving point in the rectangular coordinate plane such that the perpendicular distance from
P to
L is equal to 3, then the locus of
P is
A a sector.
B a square.
C a parabola.
D a pair of straight lines.
Two numbers are randomly drawn at the same time from nine balls numbered 1, 2, 3, 4, 5, 6, 7, 8 and 9 respectively. Find the probability that the two numbers drawn are consecutive integers.