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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
Note 
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