A force of 70 newtons acts on an area of 20cm² - Edexcel - GCSE Maths - Question 7 - 2018 - Paper 2

After the changes, the new values are:

• New Force = 70 N + 10 N = 80 N
• New Area = 20 cm² + 10 cm² = 30 cm²

Now we can find the new pressure:

Using the updated values in the pressure formula:

New Pressure = ( P = \frac{F}{A} )

[ P_{new} = \frac{80 \text{ N}}{30 \text{ cm}^2} = \frac{80}{30} = 2.67 \text{ N/cm}^2 ]

To find the percentage decrease in pressure, we use the following formula:

[ ext{Percentage Decrease} = \left( \frac{P_{initial} - P_{new}}{P_{initial}} \right) \times 100% = \left( \frac{3.5 - 2.67}{3.5} \right) \times 100% ]

Calculating this gives: [ = \left( \frac{0.83}{3.5} \right) \times 100% \approx 23.71% ]

Since the pressure decrease is approximately 23.71%, which is greater than 20%, Helen's statement, "The pressure decreases by less than 20%" is incorrect.