DIRECT PROPORTION

DIRECT PROPORTION

• 1 MARK= writing y=kx
• substitute the x and y values to find k
• 2ND MARK= Finding k by substituting values
• 3RD MARK= re writing our equation with the k found
• 4 MARKS= answer
• y is directly proportional to x. When x= 30, y= 45 Find y when x= 40
• y= kx k is constant
• 45= k x 30
• 45/30= k
• k= 1.5
• y= 1.5x
• y= (1.5)(40)
• y= 60

DIRECT PROPORTION

• The voltage , V volts, across an electrical circuit is directly proportional to the current, I amps, flowing through the circuit.
• When I= 1.2, V= 78
• a) Express V in terms of I
• V= kI K= constant
• 78= (k)(1.2)
• 78/1.2= k
• k= 65
• V= 65I
• b) Find V when I= 2
• V= (65)(2)
• V= 130 volts
• c) Find I when V= 162.5
• 162.5 = 65I
• 162.5/65= I
• I= 2.5 amps
• E is directly proportional ( fish sign) to k
• k= constant of proportionality

DIRECT PROPORTION