If accuracy is not a problem the most simple way to produce 20 ml of a 1:400 dilution is to take 1:400 of 20 ml (i.e. 0.05 ml) of the original solution and add 19.95 ml of liquid.
As pipettes are the most precise close to their maximum uptake volume and micro-pipettes are inherently much less precise than pipettes for larger volumes I'd do a two-step dilution.
1. step: 1.000 ml of original solution with 1 ml pipette + 4 times 4.750 ml with 5 ml pipette
2. step: 1.000 ml of solution from step 1 + 4 times 4.750 ml with 5 ml pipette.
When 0.25 ml is diluted to a final volume of 20 ml, the resulting dilution can be calculated as the ratio of the original volume to the final volume. This is calculated as 0.25 ml / 20 ml, which simplifies to a dilution factor of 1:80. Therefore, the resulting dilution is 1:80.
1 ml solute to 19 mls solvent. This gives a total volume of 20 (20 fold)
20 reams or 10,000 sheets of 20 lb paper would weigh approximately 100 pounds.
To prepare a 250 ppm bleach solution, you can dilute a standard household bleach (which typically contains around 5.25-6.15% sodium hypochlorite) in water. First, calculate the volume of bleach needed; for example, mix 1 part bleach with 20 parts water (1:20 dilution) to achieve approximately 250 ppm. Always add bleach to water, not the other way around, to ensure safety, and wear gloves and eye protection while handling. Make sure to label the solution and store it safely.
The mass of the substance is 20 grams in a 10 ml sample. Therefore, the substance has a density of 2 grams/ml. For a 200 ml sample of the same substance, the mass would be 400 grams (200 ml x 2 grams/ml).
Add 2 mL of culture to 20 mL of buffer. 2/20 = 1/10
400x1.20=480
400 ÷ 20 = 20 hours (though it is unlikely that the speed would be constant!)
100
0.05
400
When 0.25 ml is diluted to a final volume of 20 ml, the resulting dilution can be calculated as the ratio of the original volume to the final volume. This is calculated as 0.25 ml / 20 ml, which simplifies to a dilution factor of 1:80. Therefore, the resulting dilution is 1:80.
20 and -20
It would be a 20 by 20 ft square
20 out of 400, as a percentage = 100*(20/400) = 5%
To achieve a 20 to 1 dilution ratio in a laboratory setting, you would mix 1 part of the substance you want to dilute with 19 parts of the diluent (usually water or another solvent). This will result in a total of 20 parts, with the original substance being diluted by a factor of 20.
400 - 20 = 380