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WE:Engineering (Energy and Utilities)
Re: Roma was watering her garden with the help of a watering can. On the f
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04 Jan 2022, 12:22
Here is the OE
Solution:
Step 1: Understand Question Statement
• Roma was watering her garden.
• On the first plant, she poured 15% of the water in the can.
• On the second plant she poured 25% of water in the can.
• On the third plant she further poured 30 % of the remaining water
We need to find the value of \(\frac{water\ left\ inside\ the\ can\ after\ watering\ all\ three\ plants}{water\ inside\ the\ can\ just\ before\ watering\ the\ second\ plant}\ast100\)
Step 2: Define Methodology
We will apply the concept of successive % decrease to solve the given problem.
Step 3: Calculate the final answer
• Let us assume that the amount of water inside the can, just before watering the second plant is x.
• So, water left after watering the second plant = (100- 25 = 75) % of x =\(\frac{3}{4}x\)
• Water left after watering the third plant = (100 – 30) % of \(\frac{3}{4}x\) = \(\frac{7}{10}\ast\frac{3}{4}x\)=\(\frac{21}{40}x\)
• Thus, the required percentage =\( \frac{\frac{21}{40}x}{x}\ast100\)=\(\frac{21}{40}\ast100\)=\(52.5\)%
Thus, the correct answer is Option D.
Alternately,
We can use successive percentage change formula to solve this problem.
• Let us assume that the amount of water inside the can, just before watering the second plant, is x.
• Then, % decrease in x after watering the 3rd plant = (-25-30+\(\frac{\left(-25\right)\ast\left(-30\right)}{100})=(-55+7.5)=-47.5\)%
• Hence, % of x that is left after watering all 3 plant = \(100-47.5=52.5 \)%