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Which of the following expressions are equal to 30,600 ?
I. quadsum_(n=1)^(45)30 n-10
II. quadsum_(n=5)^(49)20+30(n-5)
III. quadsum_(n=2)^(46)-10+30(n-2)
A. I only
B. I and II
C. II and III
D. I, II, and III

Which of the following expressions are equal to 30,60030,600 ?\newlineI. n=14530n10\sum_{n=1}^{45} 30n-10\newlineII. n=54920+30(n5)\sum_{n=5}^{49} 20+30(n-5)\newlineIII. n=24610+30(n2)\sum_{n=2}^{46} -10+30(n-2)\newlineA. I only\newlineB. I and II\newlineC. II and III\newlineD. I, II, and III

Full solution

Q. Which of the following expressions are equal to 30,60030,600 ?\newlineI. n=14530n10\sum_{n=1}^{45} 30n-10\newlineII. n=54920+30(n5)\sum_{n=5}^{49} 20+30(n-5)\newlineIII. n=24610+30(n2)\sum_{n=2}^{46} -10+30(n-2)\newlineA. I only\newlineB. I and II\newlineC. II and III\newlineD. I, II, and III
  1. Evaluate Expression I: Evaluate Expression I: n=145(30n10) \sum_{n=1}^{45} (30n - 10) \newlineCalculation: Each term in the sum is 30n1030n - 10. Summing from n=1n=1 to n=45n=45,\newlinen=145(30n10)=30n=145n10×45 \sum_{n=1}^{45} (30n - 10) = 30\sum_{n=1}^{45} n - 10 \times 45 \newlinen=145n=45×(45+1)2=1035 \sum_{n=1}^{45} n = \frac{45 \times (45 + 1)}{2} = 1035 \newline30×1035450=31050450=30600 30 \times 1035 - 450 = 31050 - 450 = 30600
  2. Evaluate Expression II: Evaluate Expression II: n=549(20+30(n5)) \sum_{n=5}^{49} (20 + 30(n-5)) \newlineCalculation: Simplify the expression inside the sum,\newline20+30(n5)=30n150+20=30n130 20 + 30(n-5) = 30n - 150 + 20 = 30n - 130 \newlineSumming from n=5n=5 to n=49n=49,\newlinen=549(30n130)=30n=549n130×(495+1) \sum_{n=5}^{49} (30n - 130) = 30\sum_{n=5}^{49} n - 130 \times (49 - 5 + 1) \newlinen=549n=49×(49+1)24×(4+1)2=122510=1215 \sum_{n=5}^{49} n = \frac{49 \times (49 + 1)}{2} - \frac{4 \times (4 + 1)}{2} = 1225 - 10 = 1215 \newline30×1215130×45=364505850=30600 30 \times 1215 - 130 \times 45 = 36450 - 5850 = 30600
  3. Evaluate Expression III: Evaluate Expression III: n=246(10+30(n2)) \sum_{n=2}^{46} (-10 + 30(n-2)) \newlineCalculation: Simplify the expression inside the sum,\newline10+30(n2)=30n6010=30n70 -10 + 30(n-2) = 30n - 60 - 10 = 30n - 70 \newlineSumming from n=2n=2 to n=46n=46,\newlinen=246(30n70)=30n=246n70×(462+1) \sum_{n=2}^{46} (30n - 70) = 30\sum_{n=2}^{46} n - 70 \times (46 - 2 + 1) \newlinen=246n=46×(46+1)21=10351=1034 \sum_{n=2}^{46} n = \frac{46 \times (46 + 1)}{2} - 1 = 1035 - 1 = 1034 \newline30×103470×45=310203150=27870 30 \times 1034 - 70 \times 45 = 31020 - 3150 = 27870

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