- The weight of watermelon with 75% is 50 kg. what would be the weight of the same watermelon with 90% water.
The weight of the watermelon with 90% water would be 125 kg.
Tip – Find the constant solid mass. A watermelon consists of water and solid matter. The amount of solid matter stays exactly the same when the water content changes.
Initial total weight:
Initial water percentage= 90%
Solid percentage= 100%-90% = 10%
New water percentage= 75%
Solid percentage= 100%- 75%=25%
New Total weight = 50 kg
Weight of solid mass = 50 x 0.25 = 12.5 kg
So the initial solid mass weight would also be 12,5 kg.
So the initial weight of watermelon would be =
.10 x 12.5 = 125kg.
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2. A shopkeeper marks the price 20% higher and then increases it by another 5%. Find the total profit percentage.
1. Assume Cost Price as ₹.100.
Let the original cost price be ₹.100.
First Increase
The shopkeeper marks the price 20% higher.
First marked price =100+(20% of 100)
=100+20=120
Second Increase
The shopkeeper increases this new price by another 5%.
Final selling price =120+(5% of 120)
=120+6=126
Total Profit = SP – CP
126 – 100 = ₹. 26
The profit percentage is calculated based on the original cost price.
Profit percentage= Profit / CP x 100
26/100 x 100= 26%
Successive increase shortcut method =
Profit % = ( x+y + xy /100)
20+ 5 + 20×5 / 100
20+ 5 + 1 = 26 %
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₹. 8000 compounded half yearly at annual rate of 10% for 1 year. Find the final amount.
Solution :
Principal = ₹. 8000
Rate is equal to 10% per annum
Compounded half yearly = 10% / 2 = 5%
The number of periods in one year is equal to 2.
Formula for half yearly compounded amount
Tip – For half yearly r is taken as r/2 and n is considered as 2 halves = 2
A = P (1 + r/2/100) ^n
A = 8000 x (1 + 0.05)^2 = 8000 x 1.1025 =₹. 8820
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