Given cost of money R = 10%: discount factor $V = \bigg(\dfrac{1}{1+R}\bigg)^{1-N}$, where N is the year.
Machine A: Cost price = Rs. 25000
Year |
Running Cost |
Discount Factor $(V)^{R-1}$ |
Discounted running cost |
Σ Discounted Costs |
Total costs (cost price + Σ costs) |
$$\sum_{R=1} ^N V^{R-1}$$ |
Weighted Average annual cost |
1 |
4000 |
1 |
4000 |
4000 |
29000 |
1 |
29000 |
2 |
4000 |
0.9091 |
3636.36 |
7636.36 |
32636.36 |
1.9091 |
17095.16 |
3 |
4000 |
0.8264 |
3305.8 |
10942.14 |
35942.15 |
2.7355 |
13139.15 |
4 |
4000 |
0.7513 |
3005.26 |
13947.14 |
38947.4 |
3.4868 |
11170 |
5 |
4000 |
0.6830 |
2732.05 |
16679.2 |
41679.2 |
4.1698 |
9995.5 |
6 |
5000 |
0.6209 |
3104.6 |
19783.8 |
44783.8 |
4.7907 |
9348 |
7 |
6000 |
0.5645 |
3386.84 |
23170.64 |
48170.64 |
5.3552 |
8995.11 |
8 |
7000 |
0.5131 |
3592.1 |
26762.75 |
51762.75 |
5.8683 |
8820.74 |
9 |
8000 |
0.4665 |
3732.06 |
30494.81 |
55494.81 |
6.3348 |
8760.31 |
10 |
9000 |
0.4241 |
3816.88 |
34311.7 |
59311.7 |
6.7589 |
8775.34 |
Machine B: Cost prince = Rs. 12500
Year |
Running Cost |
Discount Factor $(V)^{R-1}$ |
Discounted running cost |
Σ Discounted Costs |
Total costs (cost price + Σ costs) |
$$\sum_{R=1} ^N V^{R-1}$$ |
Weighted Average annual cost |
1 |
6000 |
1 |
6000 |
6000 |
18500 |
1 |
18500 |
2 |
6000 |
0.9091 |
5454.6 |
11454.6 |
23654.6 |
1.9091 |
12547.6 |
3 |
6000 |
0.8264 |
4958.4 |
16413 |
28913 |
2.7355 |
10569.55 |
4 |
6000 |
0.7513 |
4507.8 |
20920.8 |
33420.8 |
3.4868 |
9584.95 |
5 |
6000 |
0.6830 |
4098 |
25018.8 |
37518.8 |
4.1698 |
8997.75 |
6 |
6000 |
0.6209 |
3275.4 |
28744.2 |
41244.2 |
4.7907 |
8608.86 |
7 |
7000 |
0.5645 |
3951.5 |
32695.7 |
45195.7 |
5.3552 |
8439.6 |
8 |
8000 |
0.5131 |
4104.8 |
36800.5 |
49300.5 |
5.8683 |
8401.16 |
9 |
9000 |
0.4665 |
4198.5 |
40999 |
53499 |
6.3348 |
8445.25 |
Machine B has a lower weighted average annual cost, and hence it should be purchased.