Math: How to convert between fraction and decimal on the Casio fx-991ES PLUS C

Tutoring math, you notice the peculiarities of scientific calculators. The tutor brings up one about the Casio fx-991ES PLUS C.

If you enter the operation 14÷9 into the Casio fx-991ES PLUS C, you’ll just as likely see 14/9 on the screen. If you want the decimal, just press the S⇔D key.

You can keep pressing the S⇔D key to toggle through various formats of the answer.

HTH:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Grapes to raisins: the condensation ratio

Tutoring math, all kinds of relationships might call out to you. The tutor brings up the water loss from grape to raisin.

According to one source, fresh grapes contain 1g fibre per 138g. According to another source, raisins contain 1g fibre per 40g.

Therefore, assuming the only loss from grape to raisin is water, 98g of 138g is lost as grapes become raisins. The percentage weight loss is 98/138 = 71%.

Neat, eh?

Source:

www.sun-world.com

no name® Thompson seedless raisins package

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator usage, math: logs in variable bases with the Casio fx-991ES PLUS C

Tutoring math, you come to appreciate calculators. The tutor points out an interesting feature on the Casio fx-991ES PLUS C.

Typically, the log key on a calculator means “base 10 log”, aka “common log.” What about base 7 log, for instance?

The Casio fx-991ES PLUS C has a log□ key which can accept an input for the base.

Example: On the Casio fx-991ES PLUS C, evaluate log762.

Solution:

  1. Press the log□ key, second down on the right.
  2. Press 7, then arrow over once, then key 62, then arrow out of the brackets.
  3. Press =

Everyone not blessed with the Casio fx-991ES PLUS C can just enter log62/log7 =

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Estimation of expected value: why sample mean is usually preferred over median

Tutoring statistics, mean is used more than median. The tutor points out a reason why.

In my post from November 30, 2014, I write about why the median might be preferred to the mean in some cases. For instance, the median tends to be less sensitive to outliers. Why, then, is the mean typically preferred in academic statistics?

The estimator of the median, it turns out, has higher variance than that of the mean. In particular,

var (sample median) = (π/2)*var(x)

Therefore, if you want to estimate the true expected value of the population, a sample size of 157 is needed to estimate it as precisely from the median as you can from a sample size of 100 using the mean.

HTH:)

Source:

Harnett, Donald L. and James L. Murphy. Statistical Analysis for Business and Economics. Don Mills: Addison Wesley, 1986.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator usage: the ENG feature on the Casio fx-991ES PLUS C

Tutoring math, calculator features are always topical. The tutor mentions the ENG function on the Casio fx-991ES PLUS C.

Back in my Halloween, 2015 post, I explain the general idea of the ENG function – that engineers and technicians often like to refer to measurements in “thousand” groupings. For instance, 1249W is 1.249kW; 0.067A is 67mA.

Example: convert 0.78A to mA

  1. Key 0.78 = (you must press = for this to work)
  2. Press ENG: hopefully you see 780×10-3

Example: convert 1249W to kW.

Solution: to go up to the bigger unit, use SHIFT ENG, like so:

  1. Key 1249 = (once again, you must press =)
  2. Press SHIFT then ENG. Hopefully you see 1.249×103

HTH:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator usage: finding final price after discount and tax with the HP-10B

Tutoring financial math, you might often use the HP-10B. The tutor shows how easily it can apply a discount then add tax to get the final price.

Example: Imagine a handbag is regular price $85 but is discounted by 20%. Assuming 12% sales tax, find final price using the HP-10B.

Solution:

  1. Key in 85
  2. Key in – 20 % =
  3. Key in + 12 % =

HTH:)

Source:

Hewlett-Packard HP-10B Business Calculator Owner’s Manual. Corvallis: Hewlett-Packard, 1994.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator usage: markup on the HP-10B

Tutoring financial math, you might fall in love with a calculator. The tutor tells about markup on the HP-10B.

Example: Imagine you buy a product for $35, then want to apply a 25% markup. Find the tag price using the HP-10B.

Solution:

  1. Key in 35 then CST
  2. Key in 25 then the orange key then MAR
  3. Press PRC

HTH:)

Source:

Hewlett-Packard HP-10B Business Calculator Owner’s Manual. Corvallis: Hewlett-Packard, 1994.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator usage: memory on the HP-10B

Tutoring financial math, you’ll likely encounter the capable HP-10B. The tutor tells how to use its user-accessible memory.

The HP-10B seems to have 11 dedicated places to store your own numbers. The locations are at 0 to 9, plus there is the M register.

Example: On the HP-10B, store the number 65.21 in register 5.

  1. Key in 65.21
  2. Press the orange key
  3. Press RCL
  4. Press 5

To retrieve the number,

  1. Press RCL
  2. Press 5

HTH:)

Source:

Hewlett-Packard Business Calculator HP-10B Owners Manual. Corvallis: Hewlett-Packard, 1994.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator usage: converting from rectangular to polar coordinates using the Casio fx-991ES PLUS C

Tutoring math, you encounter the differences between calculators even from the same manufacturer. Now, the tutor shows how to convert from rectangular to polar coordinates using the Casio fx-991ES PLUS C.

In my post from May 18 I show how to convert from rectangular to polar coordinates using the Casio fx-260solar. Here’s how to do the same with the Casio fx-991ES PLUS C:

Example: Convert (-80,-56) to polar coordinates using the Casio fx-991ES PLUS C.

Solution:

Key in SHIFT + -80 SHIFT ) -56 ) =

Across the bottom, the length (r) will show first; arrow over to see θ.

HTH:)

Source:

Casio fx-991ES PLUS C User’s Guide.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator usage: how to convert rectangular coordinates to polar with the Casio fx-260solar

Tutoring calculus, you cover polar coordinates. The tutor shows how to convert from rectangular to polar coordinates on the Casio fx-260solar.

Example:

Convert the coordinates (-56,12) to polar with the Casio fx-260solar.

Solution:

  1. Key in 56 +/- SHIFT + 12 =
  2. Hopefully you get 57.27, which is the length.
  3. Now key in SHIFT, then the left bracket key.
  4. Hopefully you get 167.9, which is the angle in degrees.

HTH:)

Source:

Casio fx-260solar manual

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.