Practice focused topic-wise MCQs with answers and explanations for quick revision and exam preparation.
Difficulty select karke sirf is topic ke focused MCQs practice karein. Score, timer aur explanations student-friendly flow me milenge.
Showing 131-140 of 600 questions.
What will be the sum of the first (65) natural numbers?
C. (2145)
\(S_{65}=\frac{65\cdot66}{2}=2145\)। (66) का आधा (33) लेकर \(65\cdot33\) करें। / \(S_{65}=\frac{65\cdot66}{2}=2145\). Take half of (66) as (33) and calculate \(65\cdot33\).
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Which is the sum of the first (70) natural numbers?
C. (2485)
\(S_{70}=\frac{70\cdot71}{2}=2485\)। (70) का आधा (35) लेकर गुणा करें। / \(S_{70}=\frac{70\cdot71}{2}=2485\). Take half of (70) as (35) and multiply.
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What is the value of \(1+2+3+\cdots+80\)?
C. (3240)
\(S_{80}=\frac{80\cdot81}{2}=3240\)। (80) का आधा (40) लेकर \(40\cdot81\) करें। / \(S_{80}=\frac{80\cdot81}{2}=3240\). Take half of (80) as (40) and calculate \(40\cdot81\).
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How much is the sum of the first (90) natural numbers?
C. (4095)
\(S_{90}=\frac{90\cdot91}{2}=4095\)। (90) को आधा करके \(45\cdot91\) करें। / \(S_{90}=\frac{90\cdot91}{2}=4095\). Halve (90) and calculate \(45\cdot91\).
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If \(S_n=1485\), what is the value of (n)?
C. (54)
\(\frac{54\cdot55}{2}=1485\), इसलिए (n=54)। विकल्पों को सूत्र में रखकर मिलाएं। / \(\frac{54\cdot55}{2}=1485\), so (n=54). Match the options by putting them in the formula.
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If the sum of the first (n) natural numbers is (2145), what is (n)?
C. (65)
\(\frac{65\cdot66}{2}=2145\), इसलिए (n=65)। सही विकल्प को सूत्र से सत्यापित करें। / \(\frac{65\cdot66}{2}=2145\), so (n=65). Verify the correct option using the formula.
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If \(S_n=3240\), how much is (n)?
C. (80)
\(\frac{80\cdot81}{2}=3240\), इसलिए (n=80)। ऐसे प्रश्नों में विकल्प जांचना सरल रहता है। / \(\frac{80\cdot81}{2}=3240\), so (n=80). In such questions, checking options is simple.
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If \(S_n=4095\), what is the correct value of (n)?
C. (90)
\(\frac{90\cdot91}{2}=4095\), इसलिए (n=90)। उत्तर को सूत्र से एक बार जरूर जांचें। / \(\frac{90\cdot91}{2}=4095\), so (n=90). Check the answer once with the formula.
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A child found the sum of natural numbers from (1) to (54). What is the correct sum?
C. (1485)
(1) से (54) तक का योग \(S_{54}=1485\) है। अंतिम संख्या को (n) मानकर सूत्र लगाएं। / The sum from (1) to (54) is \(S_{54}=1485\). Take the last number as (n) and apply the formula.
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A table contains numbers from (1) to (58). What is their sum?
C. (1711)
\(S_{58}=\frac{58\cdot59}{2}=1711\)। (1) से शुरू होने वाली सूची में प्राकृतिक संख्या योग सूत्र लगाएं। / \(S_{58}=\frac{58\cdot59}{2}=1711\). For a list starting from (1), use the natural-number sum formula.
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