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- Question
Which of the following statements is not correct?
Options- A. log10 10 = 1
- B. log (2 + 3) = log (2 x 3)
- C. log10 1 = 0
- D. log (1 + 2 + 3) = log 1 + log 2 + log 3
- Correct Answer
- log (2 + 3) = log (2 x 3)
Explanation(a) Since loga a = 1, so log10 10 = 1.(b) log (2 + 3) = log 5 and log (2 x 3) = log 6 = log 2 + log 3
∴ log (2 + 3) ≠ log (2 x 3)
(c) Since loga 1 = 0, so log10 1 = 0.
(d) log (1 + 2 + 3) = log 6 = log (1 x 2 x 3) = log 1 + log 2 + log 3.
So, (b) is incorrect.
More questions
- 1. A pipe can fill a cistern in 12 minutes and another pipe can fill it in 15 minutes, but a third pipe can empty it in 6 minutes. The first two pipes are kept open for 5 minutes in the beginning and then third pipe is also opened. In what time is the cistern emptied?
Options- A. 30 min.
- B. 33 min.
- C. 371 / 2 min.
- D. 45 min. Discuss
Correct Answer: 45 min.
Explanation:
Part filled in 5 min. = 5 x (1/12 + 1/15) = 5 x 9/60 = 3/4
Part emptied in 1 min. (when all the pipes are opened) = 1/6 - (1/12 + 1/15) = (1/6 - 3/20) = 1/60
Now, 1/60 part is emptied in 1 min. 3/4 part will be emptied in (60 x 3/4) = 45 min.- 2. Two vessels A and B contain milk and water in the ratio 7 : 5 and 17 : 7 respectively. In what ratio mixtures from two vessels should be mixed to get a new mixture containing milk and water in the ratio 5 : 3?
Options- A. 1 : 2
- B. 2 : 1
- C. 2 : 3
- D. 3 : 2 Discuss
Correct Answer: 2 : 1
Explanation:
First of all we write the fraction of milk present in three mixtures. In A : 7 /12
In B : 17 /24
In combination of A and B : 5 /8
We now apply allegation rule on these fractions from figure.
So, Ratio of A: B = 2 : 1
2nd Method
Let us assume P mixture taken from first vessel and Q mixture taken from second vessel to form a new mixture.
Part of Milk in P mixture from first vessel = 7P/12
Part of Milk in Q mixture from Second vessel = 17Q/24
Part of Water in P mixture from first vessel = 5P/12
Part of Milk in Q mixture from Second vessel = 7Q/24
According to question,
After mixing the P and Q, we will get mixture.
Milk in New Mixture / Water in New Mixture = 5/3
{(7P/12) + (17Q/24 ) } /{ (5P/12) + (7Q/24) } = 5/3
{(14P + 17Q)/24 } /{ (10P + (7Q)/24 } = 5/3
{(14P + 17Q) } /{ (10P + (7Q)} = 5/3
(14P + 17Q) x 3 = 5 x (10P + (7Q)
42P + 51Q = 50P + 35Q
51Q - 35Q = 50P - 42P
8P = 16Q
P = 2Q
P/Q = 2
P : Q = 2 : 1- 3. A shopkeeper buys 26 liter of milk @ Rs. 16 per liter. He also buys from another source an inferior quality of milk @ Rs. 10 per liter. How much quantity of the later should he buy to mix it with the former so that he can sell the mixture @ Rs. 14 per liter without making any loss?
Options- A. 13 liter
- B. 12 liter
- C. 14 liter
- D. 16 liter Discuss
Correct Answer: 13 liter
Explanation:
Quantity of milk @ Rs.10 per liter / Quantity of milk @ Rs. 16 per liter = 1 / 2
So, quantity of milk @ Rs. 10 per liter = 26 / 2 = 13 liter.
2nd Method
Let us assume shopkeeper buy P liter milk of price @ Rs. 10 per liter.
Buy price of 26 liter of milk @ Rs. 16 per liter = 26 x 16
Buy price of P liter of milk @ Rs. 10 per liter = P x 10
Sell price of total milk ( P + 26 ) @ Rs. 14 per liter = 14 x ( P + 26 )
According to question there is no loss or no profit.
Then Buy Price = Sell Price
26 x 16 + P x 10 = 14 x ( P + 26 )
? 26 x 16 + 10P = 14P + 14 x 26
? 26 x 16 - 26 x 14 = 14P - 10P
? 2 x 26 = 4P
? 4P = 2 x 26
? P = 2 x 26 / 4 = 13
So, quantity of milk @ Rs. 10 per liter = 13 liter.- 4. The sum of two number is 216 and their H.C.F is 27. The numbers are?
Options- A. 54, 162
- B. 108, 108
- C. 27, 189
- D. None of these Discuss
Correct Answer: 27, 189
Explanation:
Let the number be 27a and 27b
Then, 27a + 27b = 216
or a + b = 216/27 = 8
? Values of co-primes with sum 8 are (1, 7) and (3, 5)
So, the number are (27 x 1 , 27 x 7) i.e. (27, 189)- 5. The greatest possible length which can be used to measure exactly the lengths 7m, 3m 85cm, 12m 95 cm, is?
Options- A. 15 cm
- B. 25 cm
- C. 35 cm
- D. 42 cm Discuss
Correct Answer: 35 cm
Explanation:
Required length = H.C.F of 700, 385, 1295 cm
= 35 cm.- 6. In a class of 30 students , the average weight of boys is 20 kg and the average weight of the girls is 25 kg . The fraction of boys out of the total students of the class is
Options- A. 4/5
- B. 5/6
- C. 3/4
- D. Data insufficient Discuss
Correct Answer: Data insufficient
Explanation:
Let us assume the number of boys = B and number of girls = G.
According to question,
B + G = 30
Lets us assume total weight of boys = W1 and total weight of girls = W2
average weight of boys = total weight of boys/number of boys
total weight of boys/number of boys = 20
W1/B = 20
W1 = 20B
average weight of girls = total weight of girls/number of girls
25 = W2/G
W2 = 25G
Data is not sufficient to solve the equation.
since we do not know either the average weight of the whole class or the ratio of no. of boys to girls.- 7. The least number which when divided by 12,16 and 18 leaves 5 as remainder in each case. Find the number.
Options- A. 139
- B. 144
- C. 149
- D. 154 Discuss
Correct Answer: 149
Explanation:
Given, a = 12, b =16 , c =18, k = 5
According to the formula,
Required number =(LCM of a, b and c) + k
= (LCM Of 12, 16, 18) + 5
LCM of 12, 16, 18 is
? LCM = 2 x 2 x 3 x 4 x 3 = 144
? Required number =144 + 5 = 149- 8. P, Q and R start a business jointly. Twice the capital of P is equal to thrice the capital of Q and the capital of Q is four times the capital of R. Find the share of Q in an annual profit of ? 148500.
Options- A. ? 54000
- B. ? 64000
- C. ? 56000
- D. ? 55000 Discuss
Correct Answer: ? 54000
Explanation:
Let R's capital = 1
Then, Q's capital = 4
2 (P's capital) = 3 (Q's capital) = 3 x 4 = 12
? P's capital = 12/2 = 6
? P's share : Q's share : R's share = 6 : 4 : 1
Thus, Q's share profit = { 4/(6 + 4 + 1)} x 148500
= (4/11) x 148500
= 4 x 13500
= ? 54000- 9. The LCM of two numbers is 48. The numbers are in the ratio of 2 : 3. Find the sum of the numbers.
Options- A. 28
- B. 32
- C. 40
- D. 64 Discuss
Correct Answer: 40
Explanation:
Let numbers are 2N and 3N.
According to the question, 6N = 48
? N = 8 ( ? LCM = 6N )
? Required sum = ( 2N + 3N ) = 5N
= 5 x 8 = 40- 10. A, B and C enter into a partnership with shares in the ratio 7/2 : 4/3 : 6/5. After 4 months, A increases his share by 50%. If the total profit at the end of one year be Rs. 21600, then B's share in the profit is?
Options- A. Rs. 2100
- B. Rs. 2400
- C. Rs. 3600
- D. Rs. 4000 Discuss
Correct Answer: Rs. 4000
Explanation:
Given Ratio = 7/2 : 4/3 : 6/5 = 105 : 40 : 36
Let them initially invest Rs. 105, Rs. 40 and Rs. 36 respectively.
Ratio investment = [105 x 4 + (150% of 105) x 8] : (40 x 12) : (36 x 12)
=1680 : 480 : 432 = 35 : 10 : 9
? B's share = Rs. 21600 x (10/54) = Rs. 4000
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