S=3r^4t solve for t
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7. <u>You have $367.50 after two years.</u>
<em>Start by converting 2.5% into a decimal (divide by 100) and multiplying by 350 to find the rate of interest per year.</em>
<em>350(0.025) = 8.75</em>
<em>Since it's for two years, multiply by two. </em>
<em>8.75 x 2 = 17.5.</em>
<em>Add it on to he original, and we have</em>
<em>350 + 17.5 = 367. 5, or $367.50 when converted back to money. </em>
8. <u>The annual interest rate is 2.4%</u>
<em>find the interest rate per year: </em>
<em>120/2.5 = 48 dollars per year. this is the interest amount, we want to find the interest rate. To do this, find what % of 2000 that 48 is equal to. </em>
<em>Set up a system of equations and cross multiply.</em>
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<em>2000x = 48(100) > 2000x = 4800</em>
<em>2000</em><em>/2000</em><em>x = 4800</em><em>/2000 > </em><em>x = 2.4</em>
<em>So, the interest rate is 2.4%. </em>
9. <u>the interest paid is $300 after six months, and $600 after a year.</u>
<em>Find the interest rate, similar to problem 7. </em>
<em>3000 x 0.2 = 600. This means the interest paid is $600 a year. In six months, the total will be half, or $300.</em>
10. <u>four years.</u>
<em>Find interest rate. </em>
<em>200(0.035) = $7/year</em>
<em>Remember that value. Subtract needed from current.</em>
<em>228 - 200 = $28. </em>
<em>So, we have an interest rate of $7 a year and we need $28. Normally, we'd solve using an expression, but in this case we can use simple multiplication. Knowing that 7 x 4 = 28, We can decide that it will take four years. </em>