This is the AP \(45,42,39,\ldots\), and (S_{12}=6[90+11(-3)]=342). Exam tip: treat the decrease as a negative common difference.
Step 2
Why this answer is correct
The correct answer is C. (342). This is the AP \(45,42,39,\ldots\), and (S_{12}=6[90+11(-3)]=342). Exam tip: treat the decrease as a negative common difference.
Step 3
Exam Tip
यह \(45,42,39,\ldots\) श्रेणी है और (S_{12}=6[90+11(-3)]=342)। परीक्षा में कमी को ऋणात्मक सार्व अंतर मानें।
This is an AP with (a=5000), (d=350), (n=36), and the total is (400500). In word problems, treat each amount as a term.
Step 2
Why this answer is correct
The correct answer is C. (400500). This is an AP with (a=5000), (d=350), (n=36), and the total is (400500). In word problems, treat each amount as a term.
Step 3
Exam Tip
यह (a=5000), (d=350), (n=36) वाली AP है और कुल योग (400500) है। शब्द-प्रश्न में राशि को पद मानें।
This is an AP with (a=3200), (d=225), (n=30), and the total is (193875). In word problems, treat each amount as a term.
Step 2
Why this answer is correct
The correct answer is C. (193875). This is an AP with (a=3200), (d=225), (n=30), and the total is (193875). In word problems, treat each amount as a term.
Step 3
Exam Tip
यह (a=3200), (d=225), (n=30) वाली श्रेढ़ी है और कुल योग (193875) है। शब्द-प्रश्न में राशि को पद मानें।
This is an AP with (a=2200), (d=175), (n=24), and the total is (101100). In word problems, treat each amount as a term.
Step 2
Why this answer is correct
The correct answer is A. (101100). This is an AP with (a=2200), (d=175), (n=24), and the total is (101100). In word problems, treat each amount as a term.
Step 3
Exam Tip
यह (a=2200), (d=175), (n=24) वाली श्रेढ़ी है और कुल योग (101100) है। शब्द-प्रश्न में राशि को पद मानें।
This is an AP with (a=1500), (d=250), (n=18), and the total is (65250). In word problems, treat each amount as a term.
Step 2
Why this answer is correct
The correct answer is A. (65250). This is an AP with (a=1500), (d=250), (n=18), and the total is (65250). In word problems, treat each amount as a term.
Step 3
Exam Tip
यह (a=1500), (d=250), (n=18) वाली श्रेढ़ी है और कुल योग (65250) है। शब्द-प्रश्न में राशि को पद मानें।
This is the AP \(15,20,25,\ldots\), and the sum for (14) days is (665) minutes. In word problems, treat days as the number of terms.
Step 2
Why this answer is correct
The correct answer is C. (665). This is the AP \(15,20,25,\ldots\), and the sum for (14) days is (665) minutes. In word problems, treat days as the number of terms.
Step 3
Exam Tip
यह \(15,20,25,\ldots\) श्रेढ़ी है और (14) दिनों का योग (665) मिनट है। शब्द-प्रश्न में दिन को पदों की संख्या मानें।
This is an AP with (a=500), (d=100), (n=12), and the total is (12600). In real-life questions, treat each amount as a term.
Step 2
Why this answer is correct
The correct answer is A. (12600). This is an AP with (a=500), (d=100), (n=12), and the total is (12600). In real-life questions, treat each amount as a term.
Step 3
Exam Tip
यह (a=500), (d=100), (n=12) वाली श्रेढ़ी है और कुल योग (12600) है। वास्तविक जीवन प्रश्नों में राशि को पद मानें।
The eighteenth row has (229) bricks, so the total is (S_{18}=\frac{18}{2}(25+229)=2286). In word problems, convert the pattern into an arithmetic progression.
Step 2
Why this answer is correct
The correct answer is D. (2286). The eighteenth row has (229) bricks, so the total is (S_{18}=\frac{18}{2}(25+229)=2286). In word problems, convert the pattern into an arithmetic progression.
Step 3
Exam Tip
अठारहवीं पंक्ति में (229) ईंटें हैं, इसलिए कुल (S_{18}=\frac{18}{2}(25+229)=2286) है। शब्द-प्रश्न में क्रम को समांतर श्रेणी में बदलें।
The tenth row has (395) chairs, so the total is (S_{10}=\frac{10}{2}(80+395)=2375). Treat rows as the number of terms.
Step 2
Why this answer is correct
The correct answer is C. (2375). The tenth row has (395) chairs, so the total is (S_{10}=\frac{10}{2}(80+395)=2375). Treat rows as the number of terms.
Step 3
Exam Tip
दसवीं पंक्ति में (395) कुर्सियाँ हैं, इसलिए कुल (S_{10}=\frac{10}{2}(80+395)=2375) है। पंक्तियों को पदों की संख्या मानें।
The twelfth deposit is (265) rupees, so the total is (S_{12}=\frac{12}{2}(45+265)=1860) rupees. Keep the unit in mind in money questions.
Step 2
Why this answer is correct
The correct answer is B. (1860). The twelfth deposit is (265) rupees, so the total is (S_{12}=\frac{12}{2}(45+265)=1860) rupees. Keep the unit in mind in money questions.
Step 3
Exam Tip
बारहवाँ जमा (265) रुपये है, इसलिए कुल (S_{12}=\frac{12}{2}(45+265)=1860) रुपये है। राशि वाले प्रश्न में इकाई ध्यान रखें।
The eighteenth row has (143) bricks, so the total is (S_{18}=\frac{18}{2}(24+143)=1503). In word problems, treat rows as terms.
Step 2
Why this answer is correct
The correct answer is D. (1503). The eighteenth row has (143) bricks, so the total is (S_{18}=\frac{18}{2}(24+143)=1503). In word problems, treat rows as terms.
Step 3
Exam Tip
अठारहवीं पंक्ति में (143) ईंटें हैं, इसलिए कुल (S_{18}=\frac{18}{2}(24+143)=1503) है। शब्द-प्रश्न में पंक्तियों को पद मानें।
The tenth deposit is (825) rupees, so the total is (S_{10}=\frac{10}{2}(150+825)=4875) rupees. Do not forget the unit in money problems.
Step 2
Why this answer is correct
The correct answer is B. (4875). The tenth deposit is (825) rupees, so the total is (S_{10}=\frac{10}{2}(150+825)=4875) rupees. Do not forget the unit in money problems.
Step 3
Exam Tip
दसवाँ जमा (825) रुपये है, इसलिए कुल (S_{10}=\frac{10}{2}(150+825)=4875) रुपये है। राशि वाले प्रश्न में इकाई न भूलें।
The fifteenth term is (96), so the total is (S_{15}=\frac{15}{2}(12+96)=810) fruits. Treat the number of days as the number of terms.
Step 2
Why this answer is correct
The correct answer is C. (810). The fifteenth term is (96), so the total is (S_{15}=\frac{15}{2}(12+96)=810) fruits. Treat the number of days as the number of terms.
Step 3
Exam Tip
पंद्रहवाँ पद (96) है, इसलिए कुल (S_{15}=\frac{15}{2}(12+96)=810) फल हैं। दिनों की संख्या को पदों की संख्या मानें।
The sixteenth row has (78) seats, so the total is (S_{16}=\frac{16}{2}(18+78)=768). In word problems, treat rows as terms.
Step 2
Why this answer is correct
The correct answer is A. (768). The sixteenth row has (78) seats, so the total is (S_{16}=\frac{16}{2}(18+78)=768). In word problems, treat rows as terms.
Step 3
Exam Tip
सोलहवीं पंक्ति में (78) सीटें हैं, इसलिए कुल (S_{16}=\frac{16}{2}(18+78)=768)। शब्द-प्रश्न में पंक्तियों को पद मानें।
This is the sum of the first (9) multiples of (7), so \(7\times45=315\). Treat the number of shelves as the number of terms.
Step 2
Why this answer is correct
The correct answer is B. (315). This is the sum of the first (9) multiples of (7), so \(7\times45=315\). Treat the number of shelves as the number of terms.
Step 3
Exam Tip
यह (7) के पहले (9) गुणजों का योग है, इसलिए \(7\times45=315\)। शेल्फों की संख्या को पदों की संख्या मानें।
The tenth term is (51), so the total is (S_{10}=\frac{10}{2}(6+51)=285) plants. The same sum formula works in real situations.
Step 2
Why this answer is correct
The correct answer is B. (285). The tenth term is (51), so the total is (S_{10}=\frac{10}{2}(6+51)=285) plants. The same sum formula works in real situations.
Step 3
Exam Tip
दसवाँ पद (51) है, इसलिए कुल (S_{10}=\frac{10}{2}(6+51)=285) पौधे होंगे। वास्तविक स्थितियों में भी योग सूत्र वही रहता है।