Samacheer Kalvi 8th Maths Guide Chapter 4 Life Mathematics Ex 4.5
Samacheer Kalvi 8th Maths Guide Chapter 4 Life Mathematics Ex 4.5
Tamilnadu Samacheer Kalvi 8th Maths Solutions Chapter 4 Life Mathematics Ex 4.5
Question 1.
Question 6.
If 32 men working 12 hours a day can do a work in 15 days, then how many men working 10 hours a day can do double that work in 24 days?
Answer:
| Days (D) | Hours (H) | Men (P) |
| 15 | 12 | 32 |
| 24 | 10 | x |
Let
P1 = 32
P2 = x
H1 = 12
H2 = 10
D1 = 15
D2 = 24
W1 = 1
W2 = 1
x = 24 persons
To complete the same work 24 men needed.
To complete double the work 24 × 2 = 48 men are required.
Question 12.
Find the rate of compound interest at which a principal becomes 1.69 times itself in 2 years.
Answer:
Let principal be ‘P’
Amount is given to be 1.69 times principal
i.e 1.69 P
Time period is 2yrs. = (n)
Rate of interest = r = ?(required)
Applying the formula,
∴ rate of compound interest is 30%
Question 13.
A small – scale company undertakes an agreement to make 540 motor pumps in 150 days and employs 40 men for the work. After 75 days, the company could make only 180 motor pumps. How many more men should the company employ so that the work is completed on time as per the agreement?
Answer:
Let the number of men to be appointed more be x.
To produce more pumps more men required
∴ It is direct variation.
∴ The multiplying factor is 360/180
More days means less employees needed.
∴ It is Indirect proportion. 75
∴ The multiplying factor is 75/75
Now 40 + x = 40 × 360/180×75/75
40 + x = 80
x = 80 – 40
x = 40
40 more man should be employed to complete the work on time as per the agreement.
Question 15.
X alone can do a piece of work in 6 days and Y alone in 8 days. X and Y undertook the work for ₹ 48000. With the help of Z, they completed the work in 3 days. How much is Z’s share?
Answer:
X can do the work in 6 days.
X’s I day work = 1/6
X’s share for 1 day = 1/6 × 48000 = ₹ 800
X’s share for 3 days = 3 × 800 = ₹ 2400
Y can complete the work in 8 days.
Y’s 1 day work = 1/8
Y’s I day share = 1/8 × 4800 = ₹ 600
Y’s 3 days share = ₹ 600 × 3 = ₹ 1800
(X+Y)’s 3days share = ₹ 2400 + ₹ 1800 = ₹ 4200
Remaining money is Z’s share
∴ Z’s share = ₹ 4800 – ₹ 4200 = ₹ 600
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