In: Finance
On January 1, 2005, a person’s savings account was worth $250,000. Every month thereafter, this person makes a cash contribution of $750 to the account. If the fund is expected to be worth $500,000 on January 1, 2010, what annual rate of interest is being earned on this fund?
The answer is 11.12%
Calculations and explanations:
Here monthly payment = $750, total duration = 5 years*12 = 60 months, PV = 250,000 and FV = 500,000
The 1st contribution is made 1 month after January 1, 2005 i.e. at end of the month, Hence we can see that for January interest will be earned only on 250,000 and the contribution of 750 will not earn any interest. Closing amount at the end of January 2005 = 250,000+750+interest on 250,000
For February 2005 interest = interest rate*closing balance on January 2005. We will continue this cycle till end of December 2009.
Creating a table we get month rate = 0.927% and so annual rate = 0.927%*12 = 11.12%
Date | Beginning balance | Contribution | r (monthly) | Interest amount | Ending balance |
01 January 2005 | 250,000.00 | 750.00 | 0.927% | 2,316.94 | 253,066.94 |
01 February 2005 | 253,066.94 | 750.00 | 2,345.36 | 256,162.30 | |
01 March 2005 | 256,162.30 | 750.00 | 2,374.05 | 259,286.34 | |
01 April 2005 | 259,286.34 | 750.00 | 2,403.00 | 262,439.34 | |
01 May 2005 | 262,439.34 | 750.00 | 2,432.22 | 265,621.56 | |
01 June 2005 | 265,621.56 | 750.00 | 2,461.71 | 268,833.28 | |
01 July 2005 | 268,833.28 | 750.00 | 2,491.48 | 272,074.75 | |
01 August 2005 | 272,074.75 | 750.00 | 2,521.52 | 275,346.27 | |
01 September 2005 | 275,346.27 | 750.00 | 2,551.84 | 278,648.11 | |
01 October 2005 | 278,648.11 | 750.00 | 2,582.44 | 281,980.55 | |
01 November 2005 | 281,980.55 | 750.00 | 2,613.32 | 285,343.87 | |
01 December 2005 | 285,343.87 | 750.00 | 2,644.49 | 288,738.37 | |
01 January 2006 | 288,738.37 | 750.00 | 2,675.95 | 292,164.32 | |
01 February 2006 | 292,164.32 | 750.00 | 2,707.70 | 295,622.03 | |
01 March 2006 | 295,622.03 | 750.00 | 2,739.75 | 299,111.78 | |
01 April 2006 | 299,111.78 | 750.00 | 2,772.09 | 302,633.87 | |
01 May 2006 | 302,633.87 | 750.00 | 2,804.73 | 306,188.60 | |
01 June 2006 | 306,188.60 | 750.00 | 2,837.68 | 309,776.28 | |
01 July 2006 | 309,776.28 | 750.00 | 2,870.93 | 313,397.21 | |
01 August 2006 | 313,397.21 | 750.00 | 2,904.49 | 317,051.69 | |
01 September 2006 | 317,051.69 | 750.00 | 2,938.35 | 320,740.05 | |
01 October 2006 | 320,740.05 | 750.00 | 2,972.54 | 324,462.58 | |
01 November 2006 | 324,462.58 | 750.00 | 3,007.04 | 328,219.62 | |
01 December 2006 | 328,219.62 | 750.00 | 3,041.86 | 332,011.47 | |
01 January 2007 | 332,011.47 | 750.00 | 3,077.00 | 335,838.47 | |
01 February 2007 | 335,838.47 | 750.00 | 3,112.47 | 339,700.94 | |
01 March 2007 | 339,700.94 | 750.00 | 3,148.26 | 343,599.20 | |
01 April 2007 | 343,599.20 | 750.00 | 3,184.39 | 347,533.59 | |
01 May 2007 | 347,533.59 | 750.00 | 3,220.85 | 351,504.44 | |
01 June 2007 | 351,504.44 | 750.00 | 3,257.65 | 355,512.09 | |
01 July 2007 | 355,512.09 | 750.00 | 3,294.80 | 359,556.89 | |
01 August 2007 | 359,556.89 | 750.00 | 3,332.28 | 363,639.17 | |
01 September 2007 | 363,639.17 | 750.00 | 3,370.11 | 367,759.28 | |
01 October 2007 | 367,759.28 | 750.00 | 3,408.30 | 371,917.58 | |
01 November 2007 | 371,917.58 | 750.00 | 3,446.84 | 376,114.42 | |
01 December 2007 | 376,114.42 | 750.00 | 3,485.73 | 380,350.15 | |
01 January 2008 | 380,350.15 | 750.00 | 3,524.99 | 384,625.14 | |
01 February 2008 | 384,625.14 | 750.00 | 3,564.61 | 388,939.75 | |
01 March 2008 | 388,939.75 | 750.00 | 3,604.59 | 393,294.34 | |
01 April 2008 | 393,294.34 | 750.00 | 3,644.95 | 397,689.29 | |
01 May 2008 | 397,689.29 | 750.00 | 3,685.68 | 402,124.98 | |
01 June 2008 | 402,124.98 | 750.00 | 3,726.79 | 406,601.77 | |
01 July 2008 | 406,601.77 | 750.00 | 3,768.28 | 411,120.05 | |
01 August 2008 | 411,120.05 | 750.00 | 3,810.16 | 415,680.21 | |
01 September 2008 | 415,680.21 | 750.00 | 3,852.42 | 420,282.62 | |
01 October 2008 | 420,282.62 | 750.00 | 3,895.07 | 424,927.70 | |
01 November 2008 | 424,927.70 | 750.00 | 3,938.12 | 429,615.82 | |
01 December 2008 | 429,615.82 | 750.00 | 3,981.57 | 434,347.39 | |
01 January 2009 | 434,347.39 | 750.00 | 4,025.42 | 439,122.81 | |
01 February 2009 | 439,122.81 | 750.00 | 4,069.68 | 443,942.48 | |
01 March 2009 | 443,942.48 | 750.00 | 4,114.35 | 448,806.83 | |
01 April 2009 | 448,806.83 | 750.00 | 4,159.43 | 453,716.26 | |
01 May 2009 | 453,716.26 | 750.00 | 4,204.93 | 458,671.18 | |
01 June 2009 | 458,671.18 | 750.00 | 4,250.85 | 463,672.03 | |
01 July 2009 | 463,672.03 | 750.00 | 4,297.19 | 468,719.22 | |
01 August 2009 | 468,719.22 | 750.00 | 4,343.97 | 473,813.19 | |
01 September 2009 | 473,813.19 | 750.00 | 4,391.18 | 478,954.37 | |
01 October 2009 | 478,954.37 | 750.00 | 4,438.83 | 484,143.20 | |
01 November 2009 | 484,143.20 | 750.00 | 4,486.92 | 489,380.12 | |
01 December 2009 | 489,380.12 | 750.00 | 4,535.45 | 494,665.57 | |
01 January 2010 | 494,665.57 | 750.00 | 4,584.43 | 500,000.00 |