Pre-reg Q&As: calculation question - May 5



Multiple Completion


Directions:  For the question below, ONE or MORE of the responses is (are) correct. Decide which of the responses is (are) correct. Then choose:


A if 1,2 and3 are correct


B if 1 and 2 only are correct


C if2 and 3 only are correct


D if 1 only is correct


E if 3 only is correct


Directions Summarised
1 only
3 only

You are working in a hospital pharmacy department. You receive the following prescription for a child:

Thyroxine suspension 37.5 micrograms/ 5ml
Dose: 5ml daily
20 days supply

The formula sheet that you will work to reads as follows:

Thyroxine 50 microgram tablets        sufficient quantity
Compound Tragacanth Powder         10g
Syrup                                                 10ml
Double Strength Chloroform Water    25ml
Purified Water                                     to 50ml

You have in stock Concentrated Chloroform Water, but not Double Strength Chloroform Water.   

Which of the following statements is/are correct?

A.    The number of thyroxine 50 microgram tablets required is 15

B.     The volume of Concentrated Chloroform Water required is 0.625ml

C.     The total volume of the suspension to be supplied is 2.5ml


1. D

Total volume of suspension to be supplied = 20 x 5ml = 100ml, so C is incorrect

Total number of tablets required = 37.5 x 20 = 15, so A is correct

Volume of Concentrated Chloroform Water:
Ratio of concentration of Concentrated Chloroform Water to Double Strength Chloroform Water = 1 in 20, therefore require: 25 = 1.25ml, so B is incorrect

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Your Comments
Sean Whelan, Other healthcare professional
Posted on 5 May 2011.
The volume of conc chloroform water should be 2.5ml since the final volume needs to be 100ml not 50ml as in the original formula.
K Howell, Community pharmacist
Posted on 09/05/11 13:25 in reply to Sean Whelan.
Vishal Mistry says "I love you Sean". X
K Wong, Pre-reg graduate
Posted on 10/05/11 22:45 in reply to Sean Whelan.
S S Locum, Locum pharmacist
Posted on 12 May 2011.
Instead of wrecking your brains and getting paid peanuts for being a pharmacist, you should become a pharm tech. gets paid about the same as a pharmacist with no responsibilty, no university education, no need to be able to solve the above questions. lovely life !!!
Fatemeh Roozbahani, Pre-reg graduate
Posted on 19/11/11 19:53 in reply to Sean Whelan.
I agree with you. The volume of conc chloroform should be 2.5 ml.
Aisha Adnan, Community pharmacist
Posted on 10 February 2013. seeing this so late...but the answer SHOULD be 1.25ml (as calculated) for double strength chloroform....

for 20ml water we need 1ml conc. chloroform to make double strength, so for 25ml double strength (required for formula) we will need 1.25ml........

25---- 1/20 x 25 = 1.25ml
Aisha Adnan, Community pharmacist
Posted on 10/02/13 17:32 in reply to Aisha Adnan.
now,,,kill me..... it should be 2.5ml,as final volume to be supplied is 100ml, so 1.25x2=2.5

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