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 281-290 of 600 questions.
If the sum of the first (n) natural numbers is (1540), what is (n)?
C. (55)
\(\frac{55\cdot56}{2}=1540\), इसलिए (n=55)। विकल्पों को सूत्र में रखकर मिलाएं। / \(\frac{55\cdot56}{2}=1540\), so (n=55). Match the options by putting them in the formula.
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How much will be the sum of natural numbers from (71) to (80)?
B. (755)
योग \(S_{80}-S_{70}=3240-2485=755\) है। यह (10) लगातार संख्याओं का योग है। / The sum is \(S_{80}-S_{70}=3240-2485=755\). This is the sum of (10) consecutive numbers.
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C. (225)
\(S_{20}+S_5=210+15=225\)। दोनों अलग-अलग योग निकालकर जोड़ें। / \(S_{20}+S_5=210+15=225\). Find both sums separately and add them.
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If \(S_n=2850\), what will be the value of \(S_{n-5}\)?
A. (2485)
\(2850=S_{75}\), इसलिए \(S_{70}=2485\)। पहले (n) पहचानकर (5) कम करें। / \(2850=S_{75}\), so \(S_{70}=2485\). First identify (n) and then reduce it by (5).
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If \(S_n-S_{n-1}=68\), what will be \(S_n\)?
B. (2346)
\(S_n-S_{n-1}=n\), इसलिए (n=68) और \(S_{68}=\frac{68\cdot69}{2}=2346\)। अंतर से (n) पहचानें। / \(S_n-S_{n-1}=n\), so (n=68) and \(S_{68}=\frac{68\cdot69}{2}=2346\). Identify (n) from the difference.
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What is the sum of natural numbers from (56) to (65)?
B. (605)
योग \(S_{65}-S_{55}=2145-1540=605\) है। बीच की संख्याओं के लिए घटाव विधि उपयोगी है। / The sum is \(S_{65}-S_{55}=2145-1540=605\). The subtraction method is useful for middle numbers.
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Which sum is obtained by adding (37+38) to the sum of the first (36) natural numbers?
B. \(S_{38}\)
\(S_{36}+37+38=S_{38}\) होता है। लगातार अगले पद जोड़ने से आगे का आंशिक योग मिलता है। / \(S_{36}+37+38=S_{38}\). Adding consecutive next terms gives the later partial sum.
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If \(S_n=2016\), what is the value of (n)?
C. (63)
\(\frac{63\cdot64}{2}=2016\), इसलिए (n=63)। सूत्र से विकल्पों का मिलान करें। / \(\frac{63\cdot64}{2}=2016\), so (n=63). Match the options using the formula.
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What is the difference between the sums of the first (90) and first (85) natural numbers?
C. (440)
\(S_{90}-S_{85}=4095-3655=440\)। यह (86) से (90) तक का योग है। / \(S_{90}-S_{85}=4095-3655=440\). This is the sum from (86) to (90).
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If the sum of the first (n) natural numbers is (2211), what is (n)?
B. (66)
\(\frac{66\cdot67}{2}=2211\), इसलिए (n=66)। गुणा करने से पहले सम संख्या को आधा करें। / \(\frac{66\cdot67}{2}=2211\), so (n=66). Halve the even number before multiplying.
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