A 36

A 36 g sample of the substance contains 91% water. After drying, the weight of the sample was reduced to 18 g. What percentage of water is now in the sample?

Correct result:

p₂ =  82 %

Solution:

$$\begin{gathered} m_1=36\text{ g } \\ {p}_1=91\mathrm{\%}={\displaystyle \frac{91}{100}}=0.91 \\ {m}_2=18\text{ g } \\ s=m_1\cdot (1-p_1)=36\cdot (1-0.91)={\displaystyle \frac{81}{25}}=3.24\text{ g } \\ {w}_2=m_2-s=18-3.24={\displaystyle \frac{369}{25}}=14.76 \\ {p}_2=100\cdot {\displaystyle \frac{w_2}{m_2}}=100\cdot {\displaystyle \frac{14.76}{18}}=82\mathrm{\%} \end{gathered}$$

Try another example

Showing 0 comments:

Next similar math problems:

• Water percent
  A 15 g sample of the substance contains 70% water. After drying, the weight was reduced to 9 g. What percentage of water is now in the sample?
• Acids
  70% acid was make from same acid of two different concentrations. Amount weaker acid to the stronger acid is in ratio 2:1. What was the concentration of the weaker acid, if stronger had 91% concentration?
• Alcohol
  How many cubic centimeters of 96% alcohol is needed to obtain 0.75 liter of 40% alcohol?
• Solutions, mixtures
  How many liters of 70% solution we must add to 5 liters of 30% solution to give us a 60% solution?
• Meat loses
  Meat loses 18% of its weight by smoking. How much raw meat butcher used to manufacture 35 kilos of smoked?
• Solutions
  How much 60% solution and how much 35% solution is needed to create 100 l of 40% solution?
• Acid evaporation
  How many kilograms of water do we have to evaporate from 100 kg of 32% acid to make it 80% concentration?
• Final exam
  There are 5 learners in a class that has written a final exam Aleta scored 55% vera scored 36% and Sibusiso scored 88% if Thoko scored 71% and the class average was 63%. What was Davids score as a percentage?
• Sea water
  Mixing 62 kg of sea water with 84 kg rainwater is created water containing 3.1% salt. How many percent sea water contains salt?
• Vinegar
  What percentage vinegar we get if we mix 1 if dm³ eight percent vinegar with 1.5 dm³ six percent vinegar?
• Peroxide
  How many ml 30% of peroxide (H2O2) should be poured into 100ml H2O to give a 20% solution?
• Acid solution
  By adding 250 grams of a 96% solution of sulfuric acid to its 3% solution its initial concentration was changed to 25%. How many grams of 3% of the acid were used for dilution?
• Geography tests
  On three 150-point geography tests, you earned grades of 88%, 94%, and 90%. The final test is worth 250 points. What percent do you need on the final to earn 93% of the total points on all tests?
• Mushrooms
  Mushrooms lose 90% by weight drying. How many fresh mushrooms are needed for 5 kg of dried mushrooms?
• Acid
  The barrel is 199 litres of 38% acid. How many percent acid occurs when 61 litres revoke and replace it with the same amount of water?
• Apples 2
  Dried apples contain 15% water. Fresh apples contain 80% water. How many kg of apples we need buy in order to get 3 kg of dried apples?
• Solutions, mixtures
  We have 2 liters of 20% solution available. How much 70% solution do we need to add to it to get a 30% solution?