W, X, Y and Z are four different positive integers. When X is divided by Y, the quotient is Z and the remainder is W. If W = X - 7, what is the sum of all possible values of W?
ক
19
খ
20
গ
21
ঘ
22
সঠিক উত্তর: খ
20
উত্তর
সঠিক উত্তর: খ
20
খ
ব্যাখ্যা
Question: W, X, Y and Z are four different positive integers. When X is divided by Y, the quotient is Z and the remainder is W. If W = X - 7, what is the sum of all possible values of W?
Solution: From the given information, we can write: X = YZ + W Also given: W = X - 7
X = YZ + W ⇒ X = YZ + X - 7 ⇒ 0 = YZ - 7 ∴ 7 = YZ
There are only 2 possible cases: case 1: Y = 1 and Z = 7 case 2: Y = 7 and Z = 1
case 1 yields a CONTRADICTION. If Y = 1, then we are dividing X by 1, and if we divide by 1, the remainder will always be ZERO. In other words, if Y = 1, then W = 0 So, we can definitely rule out case 1,
It must be the case that Y = 7 and Z = 1 (case 2)
So, we have: When X is divided by 7, the quotient is 1 and the remainder is W This tells us that 7 divides into X 1 time So, the possible values of X are: 7, 8, 9, 10, 11, 12 and 13 (since 7 divides into each value 1 time.
Let's check each case. If X = 7, then the remainder (W) is 0. Doesn't follow the rule.
If X = 8, then the remainder (W) is 1. Since Y = W, Doesn't follow the rule.
If X = 9, then the remainder (W) is 2. So, when X (9) is divided by 7 (Y), the quotient (Z) is 1, and the remainder (W) is 2. Follows the rule.
If X = 10, then the remainder (W) is 3. So, when X (10) is divided by 7 (Y), the quotient (Z) is 1, and the remainder (W) is 3. Follows the rule.
If X = 11, then the remainder (W) is 4. So, when X (11) is divided by 7 (Y), the quotient (Z) is 1, and the remainder (W) is 4. Follows the rule.
If X = 12, then the remainder (W) is 5. So, when X (12) is divided by 7 (Y), the quotient (Z) is 1, and the remainder (W) is 5. Follows the rule.
If X = 13, then the remainder (W) is 6. So, when X (13) is divided by 7 (Y), the quotient (Z) is 1, and the remainder (W) is 6. Follows the rule.
Sum = 2 + 3 + 4 + 5 + 6 = 20
১০.
ক
98
খ
35
গ
350
ঘ
None
সঠিক উত্তর: ঘ
None
উত্তর
সঠিক উত্তর: ঘ
None
ঘ
ব্যাখ্যা
Question:
Solution:
১১.
The number 2 - 0.5 is how many times the number 1 - 0.5?
ক
2
খ
2.5
গ
3
ঘ
3.5
সঠিক উত্তর: গ
3
উত্তর
সঠিক উত্তর: গ
3
গ
ব্যাখ্যা
Question: The number 2 - 0.5 is how many times the number 1 - 0.5?
Solution: Let, 2 - 0.5 is x times the number 1 - 0.5
So, (2 - 0.5) = x × (1 - 0.5) ⇒ 1.5 = x × 0.5 ⇒ x = 1.5/0.5 ∴ x = 3
১২.
ক
45
খ
81
গ
405
ঘ
25
সঠিক উত্তর: ঘ
25
উত্তর
সঠিক উত্তর: ঘ
25
ঘ
ব্যাখ্যা
Question:
Solution:
১৩.
If x is a positive integer and 4x - 3 = y, which of the following CANNOT be a value of y?
ক
1
খ
7
গ
13
ঘ
61
সঠিক উত্তর: খ
7
উত্তর
সঠিক উত্তর: খ
7
খ
ব্যাখ্যা
Question: If x is a positive integer and 4x - 3 = y, which of the following CANNOT be a value of y?
Solution: If x = 1: 41 - 3 = 1
If x = 2: 42 - 3 = 13
If x = 3: 43 - 3 = 61
The only value that y cannot take is 7.
১৪.
When 35 - [30 - {35 - (15 - *)}] = 60, then * is equal to-
ক
- 19
খ
35
গ
20
ঘ
- 29
সঠিক উত্তর: খ
35
উত্তর
সঠিক উত্তর: খ
35
খ
ব্যাখ্যা
Question: When 35 - [30 - {35 - (15 - *)}] = 60, then * is equal to-