QR formulas Flashcards
Mean
Average. Add up all the values and divide the total by how many there are
Median
Middle number of a set of data.
Order numerically (lowest to highest)
Mode
Number that occurs most often in a set
Range
Difference between highest and lowest
Rate problems (think of it like speed = distance/time. E.g., might have running tap, etc.) and relative speed.
When 2 things travel towards each other, we need to add the 2 velocities together .
E.g. Train 1 going east 50mph and train going west 40mph. They are 135 miles apart. How long before they collide?
t = 135miles/(40mph+50mph) = 135/90 = 1.5 hours.
When 2 things travel alongiside each other -take away their velocites together.
Compound and simple interest formula
Simple: I = P * T * R; Compound: I = P(1+r/n)^nt
Tax problems
Usually skip - time consuming, but always figure out what bracket you’re in. May involve algebra. Don’t do if too complex. Then layer/collate the tax. E.g $,65, 000 income: In this bracket, so do the brackets below that, then calculate every dollar in that particular bracket.
Dice problems
Rolling 2 dice - Total no. of permutations = 36
E.g. What is the probability of rolling 2 dice and having the 2 numbers add up to 4?
Three possibilities - 2+2, 1+3, 3+1
- (1/6 * 1/6) x 3
Therefore probability - 3/36 = 1/12
Deck of cards
Total number of cards = 52 (Without jokers)
4 Suits (Heart, club, spade, diamond)
13 cards per suit
With replacement: Total number of cards must go back to 52 and cards of interest must go back to initial amount.
Without replacement: Must decrease total number of cards by 1 and decrease number of cards of interest by 1.
E.g. Probability of pulling 3 spades in a deck without replacement?
13/52 * 12/51 * 11/50 = 33/2550
Acceleration formula
Acceleration = Change in velocity/tim
Area of a circle
πr^2 r=radius
Circumference of a circle
2πr
Area of a triangle
1/2 * base * height
Sphere Volume
(4/3)πr^3
Volume of a cylinder
πr^2 * h
Surface Area of Cylinder
2πrh+2πr^2 (round bit + 2 circles)
1/20
0.05 = 5%
1/10
0.1 = 10%
1/9
0.11 = 11%
1/8
0.125 = 12.5%
1/7
0.14 = 14%
1/6
0.17 = 17%
1/5
0.2 = 20%
1/4
0.25 = 25%
1/3
0.33 = 33%
1/2
0.5 = 50%
Percentage Change formula
(Final-Initial)/Initial * 100
Milli (could be gram, milimetre, etc.) CONVERTING FROM LARGER TO SMALLER (E.g. Meter to milimeter) = multiply. Smaller to larger = divide.
0.001 mg e.g. 1g = 1 * 1000 or 1/0.001 = 1000mg
gives you mg in 1 g.
Centi (general)
0.01 e.g. 1m = 1 * 100 or 1/0.01 = 100cm
Deci
0.1. So one deci metre is 1/10 of meter. Or it is 10cm.
Kilo
- Times and divide by 1000 (e.g kg to g)
Mega
1 Million (1,000,000). Times and divide by 1 mil. (e.g. megametre to metre).
Giga
Billion (1,000,000,000). (e.g. gigametre to metre). Subtract digits for larger units (e.g. gigameter to mega meter - divide by [taking 6 zerois) 1000]
Temperature °C to °F
(°C × 9/5) + 32 = F
1 inch in cm
2.54 cm (Estimate - 2.5cm)
1 mile in ft and km
5280 ft = 1.6km (Estimate - 5000ft and 1.5km).
1 ft in inches
12 in
1cm in mm and inches
10mm = 0.4in
1kg in g and lb
1000g = 2.2lb
1lb in g and ounces
454g = 16 ounces
1 tonne in kg and g
1000kg = 100,000g
1m^3 in litres
1000l
Area - 1m^2 in cm
10,000cm
Area - 1km^2 in cm
1,000,000m
Q
Time - Weeks and days in year
52 weeks, 365 days in a year
Hrs to mins to secs
Hrs 🠒 *60 - Mins 🠒 *60 - Secs
Secs to mins to hrs
Secs 🠒 /60 - Mins 🠒 /60 - Hrs
