Question

If you add 43 of food in 350 ml water and dilution of 1:6 is made then from this dilution 1:90 is made and from this 1 ml is added to 60 ml of water then 0.1 ml from this last dilution is plated and after incubation 143 colonies are counted what is the total count per g of original sample

Answer 1

DF = Initial dilution * Subsequent dilution * Amount Plated

Total Count Per g =
`(1)/(DF)` * Colonies Counted

Initial dilution :
`(43)/((43+350))=(43)/(393)`

Subsequent dilution :
`((1)/(6) )*((1)/(90) )*((1)/(61) )`

Amount Plated : 0.1

Colonies Counted : 143

DF =
`(43)/(393)*(1)/(6)*(1)/(90)*(1)/(61)*0.1`

DF=
`(43)/(393)*(1)/(6)*(1)/(90)*(1)/(61)*(1)/(10)`

DF =
`(43)/(129454200)`

Total Count Per g =
`((129454200)/(43) )*143`

Total Count Per g =
`4.3*10^(8)`