A2: substitute numerical values into formulae and expressions, including scientific formulae

What is substitution?

Substitution means putting numbers in place of letters to calculate the value of an expression

Substitution into formula F=(9C/5)+32. What is the temperature in Fahrenheit if it is 20 degrees C?

9×20=180, 180/5=36, 36+32=68 degrees F

The formula to work out the force in Newtons of an object is F=ma, where m is mass in kilograms and a is the acceleration of the object. What is the force of an object that has a mass of 16 kg and an acceleration of 7 m/s²?

16×7=112kgm/s² (Newtons)

Regular substitution: Work out the value of d+(3e+f)² when d=2, e=-3 and f=1 (USE BIDMAS)

3x-3=-9+1=-8, -8²=64, 2+64=66

What is the expression that has the greatest value when y = 10

2y, 31 − y, y+9, y/2

2y=20, 31-y=21, y+9=19, y/2=5

31-y is greatest

The cost of hiring a hot tub is found using the formula: Hire cost = £50 plus an extra £45 per day

(a) Work out the hire cost for hiring the hot tub for 21 days.

Alex hires the hot tub for a number of days and the cost is £545

(b) How many days did Alex hire the hot tub?

(a) 50+(45×21)=945+50=£995

(b) 545-50=495, 495/45=11 - 11 days