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Consulting Math Plain Number Calculation
Plain Number Calculation is the most basic buildingblock in improving your consulting math. At the end of the day, you need to be able to perform the stripeddown number calculations, and a lot of them.
There are 8 types of plain number calculation questions that you will mostly encounter. They can range anywhere from simple conversions to big number calculation. Honing your mental arithmetic is the key to solving them!
A quick glance
 Type 1: Percentage
 Type 2: Multiplications
 Type 3: Increase in Percentage
 Type 4: Decrease in Percentage
 Type 5: Currency ConversionFrom USD
 Type 6: Currency ConversionTo USD
 Type 7: Time Conversion
 Type 8: Big Number Comfort
As I mentioned in the Mental Math article, it’s usually acceptable to have up to 5% margin for errors, even with Plain Number Calculation. All answer keys in this practice drills are absolutely correct with 0% margin of error. In the MCP spirit, we also break down PlainNumber calculations into 8 types. By isolating each type of calculations, that brain muscle group can be practice over and over continuously to reach the growth point.
Let’s go into each one of them.
Remember that accuracy is as important (if not more) as speed. Try to be correct (meaning staying within 5% of the answer key) as many time as possible and then gradually improve your speed.
Type 1: Percentages
In a consulting context, people like to look at values, not only in absolute, but also relative to
each other. Percentages become a very useful tool.
As a consultant, you will very often find yourself doing backoftheenvelope percentage calculations either in problemsolving meetings, in client interviews, or in your own analyses. Therefore, it’s not surprising that this type of calculation is very common in Case Interviews and entrance tests (McKinsey PST & BCG Potential Test).
Practice Exercise
35% of 40,000?
20% of 1,250?
33% of 2.5 billion?
7.5% of 85?
4% of 1,340?
14,000
250
825,000,000 / 825 million
6.375
53.6
Type 2: Multiplication
Besides additions and subtractions, multiplications are another important building block of Plain Number Calculation. Multiplications are not only common in real life, but also in every aspect of business and consulting.
4 x 920?
2.5 x 3,400?
85 x 23,000?
2,350 x 8?
350 x 12?
3,680
8,500
1,955,000
18,800
4,200
Type 3: Increase in Percentage
This is a twist version of type 1 above, but it is slightly different. Let’s try some more practice with Plain Number Calculation!
900 increased by 54% would be…?
85,200 increased by 6% would be…?
2,400,000 increased by 75 % would be…?
265 increased by 0.2 % would be…?
6,200 increased by 15% would be…?
1,386
90,312
4,200,000
265.5
7130
Type 4: Decrease in Percentage
200 decreased by 45% would be…?
73,500 decreased by 8% would be…?
8,500,000 decreased by 35 % would be…?
575 decreased by 0.6 % would be…?
7,400 decreased by 22% would be…?
110
67,620
5,525,000
571.55
5,772
Plain Number Math Drills
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1000 plain calculation by types

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Type 5: Currency Conversion  From USD
The world is getting smaller and international business is increasingly common. Along with that comes the need to do crosscountry currency conversions in real consulting work. This is very common in Plain Number Calculation.
Below are the acceptable approximate conversion rates between US Dollars and the 7 most popular currencies in the world as of 2019. These conversion rates fluctuate day to day; however, there are still generallyaccepted rates in most cases. These estimates are acceptable
in Case Interviews unless the interviewer specifically instructs you to use more accurate rates.
$12,500 USD equals … JPY?
$15,000 USD equals … GBP?
$300 USD equals … EUR?
$7,500 USD equals … AUD?
$2 million USD equals … SGD?
$650 USD equals … CNY?
$25,200 USD equals … INR?
1,375,000 JPY
11,250 GBP
270 EUR
11,250 AUD
2.66 million SGD
4,550 CNY
1,764,000 INR
Type 6: Currency Conversion  To USD
A twist version of the above. The trick is to use division instead of multiplication. Let’s try a few
practice ones.
250 GBP equals to…USD?
500 EUR equal to…USD?
7,400 AUD equal to…USD?
7,020 CNY equal to…USD?
15,400 INR equal to…USD?
600,000 SGD equal to…USD?
1,250,000 JPY equal to…USD?
$333
$555
$4933
$1002
$220
$451,128
$11,364
Type 7: Time Conversion
Though not very popular in Case Interviews and entrance tests (McKinsey PST & BCG Potential Test), calculations involving time units can be very tricky and timeconsuming. Most units of time are easy to imagine and sense but very hard to do calculations with; this is because of their odd nature. There are only 60, not 100, seconds in a minute, 60, not 100, minutes in an hour, 24, not 25, hours in a day, 30, not 50, days in a month, 52, not 50, weeks in a year, etc. Being skilled in this type of calculations will add value to your interviewing and test taking skillset!
When doing this Plain Number Calculation, please note that there are two different ways to
calculate hours per week:
 24/7: There are 24 hours per day and 7 days per week.
 Standard work hour: There are 8 hours per working day, and 5 working days per week.
Assuming that there are 30 days per month and 365 days per year.
120 items per day equal to…items per hour? (24/7)
75,000 items per year equal to…items per week? (Standard work hours)
1,800 USD per month equal to …USD per day? (Standard work hours)
15 items per hour equal to…items per month? (Standard work hours)
25 USD per day equal to…USD per year? (24/7)
5 items
1,442.3 items
$90 USD
2,400 items
9,125 USD
Type 8: Big Number Comfort
When people think of Management Consulting, usually they think of big projects, big clients, and big numbers. Almost all numbers floating around each project are big: big revenue, big production volume, big number of FTE (Fulltime Equivalent) employees, big investments, big assets, etc. It is essential for all consultants to be comfortable working with big numbers. They have to be able to sense how big “big numbers” really are and perform big calculations with them.
500 thousand equals to…million?
6400 billion equals to…trillion?
1.5 trillion equals to…thousand?
0.06 trillion equals to…million?
450,000 thousand equals to… million?
0.5 million
6.4 trillion
1,500,000,000 thousand
60,000 million
450 million
Plain Number Math Drills
$ 39
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1000 plain calculation by types

PDF format. Instant access to your material

30day money back guarantee
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