Solved We daesday Simple Interest Worksheet Directions: | Chegg.com - Free Printable

Let’s solve each problem step by step using the simple interest formula:

I = P × R × T

Where:
- I = Interest (what we’re solving for in most cases)
- P = Principal (the starting amount of money)
- R = Rate (as a decimal — so 8% becomes 0.08)
- T = Time (in years — so months or days must be converted to fractions of a year)

We’ll go box by box.

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1a.

P = $500
R = 8% → 0.08
T = 3 months → 3/12 = 0.25 years

I = 500 × 0.08 × 0.25
= 500 × 0.02
= $10.00

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1b.

P = $50
R = 12% → 0.12
T = 1 month → 1/12 ≈ 0.083333...

I = 50 × 0.12 × (1/12)
= 50 × 0.01
= $0.50

*(Note: 0.12 ÷ 12 = 0.01, so 50 × 0.01 = 0.50)*

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1c.

P = $1,000
R = 18% → 0.18
T = 24 months → 24/12 = 2 years

I = 1000 × 0.18 × 2
= 1000 × 0.36
= $360.00

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1d.

P = $600
R = 15% → 0.15
T = 60 days → 60/360 = 1/6 ≈ 0.166666...

I = 600 × 0.15 × (1/6)
First: 0.15 × (1/6) = 0.025
Then: 600 × 0.025 = $15.00

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2a.

I = $6
R = 12% → 0.12
T = 3 months → 3/12 = 0.25
Find P.

Formula rearranged: P = I / (R × T)

P = 6 / (0.12 × 0.25)
= 6 / 0.03
= $200.00

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2b.

I = $15
R = 15% → 0.15
T = 90 days → 90/360 = 0.25
Find P.

P = 15 / (0.15 × 0.25)
= 15 / 0.0375
= $400.00

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2c.

I = $300
R = 12% → 0.12
T = 6 months → 6/12 = 0.5
Find P.

P = 300 / (0.12 × 0.5)
= 300 / 0.06
= $5,000.00

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2d.

I = $0.90
R = 6% → 0.06
T = 60 days → 60/360 = 1/6 ≈ 0.166666...
Find P.

P = 0.90 / (0.06 × 1/6)
First: 0.06 × (1/6) = 0.01
Then: 0.90 / 0.01 = $90.00

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3a.

I = $12
P = $200
T = 6 months → 6/12 = 0.5
Find R.

Formula: R = I / (P × T)

R = 12 / (200 × 0.5)
= 12 / 100
= 0.12 → 12%

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3b.

I = $390
P = $2,000
T = 18 months → 18/12 = 1.5
Find R.

R = 390 / (2000 × 1.5)
= 390 / 3000
= 0.13 → 13%

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3c.

I = $0.50
P = $25
T = 6 weeks → 6/52? Wait — worksheet says “(42/360)” — that’s probably a typo? But let’s follow what’s written: T = 42/360

Wait — 6 weeks is usually 42 days, and they’re using 360-day year → so T = 42/360

So:

R = 0.50 / (25 × 42/360)

First calculate denominator: 25 × 42 = 1050; 1050 / 360 = 2.916666...

Better to compute as:

R = 0.50 / (25 × 42/360)
= 0.50 × (360 / (25 × 42))
= 0.50 × (360 / 1050)
= 0.50 × 0.342857...
≈ 0.171428... → 17.1429%

But let’s do exact fraction:

R = 0.50 / (25 * 42 / 360)
= 0.50 * 360 / (25 * 42)
= 180 / 1050
= 18 / 105
= 6 / 35 ≈ 0.17142857 → 17.1429%

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3d.

I = $3
P = $50
T = 180 days → 180/360 = 0.5
Find R.

R = 3 / (50 × 0.5)
= 3 / 25
= 0.12 → 12%

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4a.

You borrowed $50, paid back $58 after 6 months.

Interest paid = 58 - 50 = $8

Time = 6 months = 0.5 years

Find rate R.

R = I / (P × T) = 8 / (50 × 0.5) = 8 / 25 = 0.32 → 32%

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4b.

Borrow $800 at 18% for 11 months.

Find total interest.

P = 800
R = 18% → 0.18
T = 11/12 years

I = 800 × 0.18 × (11/12)

First: 0.18 × 11/12 = (0.18 × 11) / 12 = 1.98 / 12 = 0.165

Then: 800 × 0.165 = $132.00

Alternatively:

800 × 0.18 = 144 (for 1 year)
For 11 months: 144 × (11/12) = 144 × 0.916666... = 132

Yes, $132.00

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Final Answer:

1a. $10.00
1b. $0.50
1c. $360.00
1d. $15.00

2a. $200.00
2b. $400.00
2c. $5,000.00
2d. $90.00

3a. 12%
3b. 13%
3c. 17.1429%
3d. 12%

4a. $8 interest, 32% rate
4b. $132.00