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Which of the following numbers is divisible by both 7 and 11?
3014
2534
2684
1771
1771
Since 7 and 11 are coprime, a number is divisible by both 7 and 11 if and only if it is divisible by their product, which is 77. Alternatively, check divisibility by 11 first using the alternating sum of digits, and then check divisibility by 7.
A set of four numbers: 3014, 2534, 2684, and 1771
LCM(7,11)=77
Since 7 and 11 are coprime, a number is divisible by both 7 and 11 if and only if it is divisible by their product, which is 77. Alternatively, check divisibility by 11 first using the alternating sum of digits, and then check divisibility by 7.
Checking divisibility by only one of the two numbers or performing long division on all four numbers without checking divisibility rules first.
Step 1: Understand the Condition
For a number to be divisible by both 7 and 11, it must be divisible by their least common multiple (LCM). Since 7 and 11 are prime numbers, their LCM is 7×11=77. Thus, we need to find which option is divisible by 77.
LCM(7,11)=77
Step 2: Check Option A (3014)
Divide 3014 by 7: 3014÷7=430.57 (not an integer). Therefore, 3014 is not divisible by 7.
3014÷7=430.57
Step 3: Check Option B (2534)
Divide 2534 by 7: 2534÷7=362 remainder 0? Let's check: 362×7=2534, wait: 362×7=2534? No, 362×7=2534 is incorrect (362×7=2534 gives 362×7=2534). Let's check division: 2534÷7=362.0 wait: 362×7=2534? Let's test 2534/7: 7×300=2100, 434/7=62, so 362. Wait, 362×7=2534. But for 11: alternating sum (4+5)−(3+2)=4, which is not divisible by 11.
2534÷11⟹Remainder 4
Step 4: Check Option C (2684)
Check divisibility by 11: alternating sum (4+6)−(8+2)=0 (divisible by 11). Now check divisibility by 7: 2684÷7=383.428 (not divisible by 7).
2684÷7=383.43
Step 5: Check Option D (1771)
Check divisibility by 11: alternating sum $(1