So, we givil II U
EXERCISE 1.1
q.
1
of the
(ii) The amount of air present in a cylinder when a vacuum pump removes
4
air remaining in the cylinder at a time.
(ii) The cost of digging a well after every metre of digging, when it costs * 150 for the
first metre and rises by * 50 for each subsequent metre.
(iv) The amount of money in the account every year, when 10000 is deposited at
compound interest at 8 % per annum.
2. Write first four terms of the AP, when the first term a and the common difference d are
given as follows:
(i) a=10, d=10
(ii) a=-2, d=0
1
(iii) a=4, d=-3
(iv) a=-1, d=
2
(v) a=-1.25, d=-0.25
3. For the following APs, write the first term and the common difference:
Answers
Answer:
(i) Fare for first km = Rs. 15
Fare for second km = Rs. 15+8= Rs 23
Fare for third km = Rs. 23+8=31
Here, each subsequent term is obtained by adding a fixed number (8) to the previous term.
Hence, it is in A.P.
(ii) Let us assume, initial quantity of air =1 .....1)
Therefore, quantity removed in first step =
4
1
Remaining quantity after first step
1−
4
1
=
4
3
....2)
Quantity removed in second step
=
4
3
×
4
1
=
16
3
Remaining quantity after second step
=
4
3
−
16
3
=
16
9
....3)
Here, each subsequent term is not obtained by adding a fixed number to the previous term.
Hence, it is not an AP.
(iii) Cost of digging of 1
st
meter =150
Cost of digging of 2
nd
meter =150+50=200
Cost of digging of 3
rd
meter =200+50=250
Here, each subsequent term is obtained by adding a fixed number (50) to the previous term.
Hence, it is an AP.
(iv) Amount in the beginning = Rs. 10000
Interest at the end of 1
st
year @ 8% = 10000×8%=800
Thus, amount at the end of 1
st
year =10000+800=10800
Interest at the end of 2
nd
year @ 8% = 10800×8%=864
Thus, amount at the end of 2
nd
year =10800+864=11664
Since, each subsequent term is not obtained by adding a fixed number to the previous term; hence, it is not an AP.
Answer:
the first answer is absolutely correct.......!!!!!