Higher January 2019 Paper 1 Q14

EdexcelHigherCurrent spec4 marksDirect & Inverse Proportion

14 \(T\) is directly proportional to the cube of \(r\)
\(T = 21.76\) when \(r = 4\)

(a) Find a formula for \(T\) in terms of \(r\) (3)

(b) Work out the value of \(T\) when \(r = 6\) (1)

Mark scheme (a)

Scheme	Marks
\(T = kr^3\)	M1
\(21.76 = k \times 4^3\) oe or \(k = 0.34\)	M1
\(T = 0.34r^3\) oe	A1
	(3)

Notes

M1: Allow \(r^3 = mT\)
Do not allow \(T = r^3\)

M1: for correct substitution into a correct equation; implies first M1
Award M2 if \(k = 0.34\) stated unambiguously (\(m = 2.94\))
Condone use of proportional sign in place of equals sign

A1: Only award if \(T\) is the subject
Award M2A1 if \(T = kr^3\) on answer line and \(k\) given as 0.34oe in working space.

Scheme	Marks
73.44	B1ft
	(1)
	(4 marks)