Math Problem Statement

a is directly proportional to b^2. a is also directly proportional to √c. When b = 3, the value of c is 162. What is the value of c when b = 5? If your answer is a decimal, then round it to 1 d.p.

Solution

Problem Analysis:

The problem states that:

  1. aa is directly proportional to b2b^2, i.e., a=k1b2a = k_1 b^2,
  2. aa is also directly proportional to c\sqrt{c}, i.e., a=k2ca = k_2 \sqrt{c}.

This implies that aa is jointly proportional to b2b^2 and c\sqrt{c}. Combining these relationships gives: a=kb2c,a = k b^2 \sqrt{c}, where kk is a constant.

We are given:

  • When b=3b = 3, c=162c = 162,
  • We need to find cc when b=5b = 5, rounded to 1 decimal place.

Step 1: Find kk using given data.

Substitute b=3b = 3, c=162c = 162 into a=kb2ca = k b^2 \sqrt{c}: a=k(32)162.a = k (3^2) \sqrt{162}. a=k(9)162.a = k (9) \sqrt{162}.

Solve for kk: k=a9162.k = \frac{a}{9 \sqrt{162}}.


Step 2: Use kk to find cc when b=5b = 5.

Using the same equation, substitute b=5b = 5: a=k(52)c.a = k (5^2) \sqrt{c}. a=k(25)c.a = k (25) \sqrt{c}.

Rearrange to solve for cc: c=ak25.\sqrt{c} = \frac{a}{k \cdot 25}. c=(ak25)2.c = \left( \frac{a}{k \cdot 25} \right)^2.


Let me calculate this step-by-step. math

Given values

b1 = 3 c1 = 162 b2 = 5

Compute k using the given values for b1 and c1

k = 1 / (b1**2 * math.sqrt(c1))

Calculate c when b = b2

c2 = (1 / (k * b2**2))**2

Round to 1 decimal place

c2_rounded = round(c2, 1) c2_roundedThe value of cc when b=5b = 5 is 21.0.

Would you like a detailed explanation of the steps or have any specific questions?

Here are five related questions to consider:

  1. How does joint proportionality affect the relationship between variables?
  2. What happens to the proportionality constant kk if aa, bb, or cc changes?
  3. How is the square root function critical in this problem?
  4. How would the solution change if aa were inversely proportional to c\sqrt{c}?
  5. Could you use this method to solve for bb given cc and aa?

Tip: Always verify units or values in real-world proportionality problems to ensure they make sense in context!

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Math Problem Analysis

Mathematical Concepts

Direct Proportionality
Joint Proportionality
Square Roots

Formulas

a = k * b^2 * √c

Theorems

Properties of Proportionality

Suitable Grade Level

Grades 10-12