Math  /  Algebra

QuestionThe ends of a bar have to be machined down until the bar is 3 m long. After 5%5 \% of the length had been removed, it was found that 0.5%0.5 \% of the new length still had to come off. What length was removed at each machining and what was the original length of the bar?

Studdy Solution

STEP 1

1. The final length of the bar is 3 meters.
2. Initially, 5% of the original length was removed.
3. After the first removal, 0.5% of the new length still needed to be removed to reach the final length.
4. We need to find the length removed at each machining and the original length of the bar.

STEP 2

1. Define variables for the original length and the lengths removed.
2. Set up equations based on the problem description.
3. Solve the equations to find the original length and the lengths removed.

STEP 3

Define variables. Let L L be the original length of the bar. Let R1 R_1 be the length removed in the first machining, and R2 R_2 be the length removed in the second machining.

STEP 4

Set up equations based on the problem description.
The first machining removed 5% of the original length: R1=0.05L R_1 = 0.05L
After the first machining, the length of the bar is LR1 L - R_1 .
The second machining removed 0.5% of the new length, and the final length is 3 meters: R2=0.005(LR1) R_2 = 0.005(L - R_1)
The total length removed is the sum of R1 R_1 and R2 R_2 , and the final length is 3 meters: LR1R2=3 L - R_1 - R_2 = 3

STEP 5

Substitute R1 R_1 and R2 R_2 into the equation and solve for L L .
Substitute R1=0.05L R_1 = 0.05L into R2 R_2 : R2=0.005(L0.05L) R_2 = 0.005(L - 0.05L) R2=0.005(0.95L) R_2 = 0.005(0.95L) R2=0.00475L R_2 = 0.00475L
Substitute R1 R_1 and R2 R_2 into the total length equation: L0.05L0.00475L=3 L - 0.05L - 0.00475L = 3 L(10.050.00475)=3 L(1 - 0.05 - 0.00475) = 3 L(0.94525)=3 L(0.94525) = 3
Solve for L L : L=30.94525 L = \frac{3}{0.94525} L3.173meters L \approx 3.173 \, \text{meters}

STEP 6

Calculate the lengths removed at each machining.
Calculate R1 R_1 : R1=0.05×3.173 R_1 = 0.05 \times 3.173 R10.15865meters R_1 \approx 0.15865 \, \text{meters}
Calculate R2 R_2 : R2=0.00475×3.173 R_2 = 0.00475 \times 3.173 R20.01507meters R_2 \approx 0.01507 \, \text{meters}
The original length of the bar was approximately 3.173meters 3.173 \, \text{meters} . The length removed at the first machining was approximately 0.15865meters 0.15865 \, \text{meters} . The length removed at the second machining was approximately 0.01507meters 0.01507 \, \text{meters} .

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