CTET Jan 2012 Paper I Math Discussion

CTET Jan 2012: Paper I

Math Section Discussion

Some riders

• Not meant for the Mathematicians!• For those who are “scared” of Math• Some of the methods discussed are strictly for

fun, yet may give astonishing results

Some Fundamentals of MCQ

• All choices except one are wrong• Framing the wrong choices takes just one

minute!– Paired choices– Units– Direction

Select one:• a. 9:59 A.M. • b. 10:01 A.M. • c. 9:59 P.M. • d. 9:57 A.M.

Choice Pair!

Then, three choices are A.M. while one is P.M.!

Now, if 9:59 A.M. is your correct answer, what choices would you frame?

Select one:• a. 9:59 A.M. • b. 10:01 A.M. • c. 9:59 P.M. • d. 9:57 A.M.

What time is 4 hours 59 minutes before 2:58 P.M.?

In which of the following divisions, will the remainder be more than the remainder you get when you divide 176 by 3?Select one:• a. 174 ÷ 4 • b. 175 ÷ 3 • c. 176 ÷ 2 • d. 173 ÷ 5

Remainders

• 176 ÷ 3 Maximum remainder is 2.• Only one correct answer.• To check, start with the highest divisor, that is,

5. • 173 ÷ 5 170 is a multiple, so remainder is 3.

Remainders…some more fundas

• Divisibility rule also gives remainder (?)• 176 ÷ 3

• 1+7+6=14; 1+4=5• Remainder will be 5 ÷ 3, that is, 2.

• Are there more divisibility rules than you know of?

More divisibility rules

• 11: Keep subtracting the last digit from the number to get a 0

• 31: Keep subtracting thrice the last digit from the number to get a 0

• 41: Keep subtracting 4 x the last digit from the number to get a 0

Can you derive more now? Is there an exception?http://mathforum.org/dr.math/faq/faq.divisibleto50.html

500 cm + 50m + 5 km =Select one:

• a. 500 m • b. 555 m • c. 5055 m • d. 55 m

Answer must be more than 5 km or

5000 m.

Sum of place values of 6 in 63606Select one:

• a. 60606 • b. 6606 • c. 6066 • d. 18

The difference of 5671 and the number obtained on reversing its digits isSelect one:• a. 4906 • b. 3916 • c. 7436 • d. 3906

Answer must be divisible by 9!

Why?

Quick way of checking divisibility?

Study the following pattern:1× 1 = 111×11 = 121111×111 = 12321.......... ..........What is 11111× 11111?Select one:• a. 123454321 • b. 12345421 • c. 123453421 • d. 1234321

Quick counting:1.How many 1’s in

each number?2.How many digits

in each product?

Which of the following is correct?Select one:• a. Predecessor of successor of 1000 is 1000. • b. Predecessor of predecessor of 1000 is 999. • c. Successor of predecessor of 1000 is 1001. • d. Successor of predecessor of 1000 is 1002.

A shop has 239 toys. Seventy more toys were brought in. then 152 of them were sold. The number of toys left wasSelect one:• a. 239 + 70+ 152 • b. 239 – 70 + 152 • c. 239 + 70 – 152 • d. 239 – 70 – 152

A pencil costs two and a half rupees. Amit buys one and a half dozen pencils and gives a 100 rupee note to the shopkeeper. The money he will get back isSelect one:• a. Rs. 45 • b. Rs. 65 • c. Rs. 30 • d. Rs. 55

In the product 3759 × 9573, the sum of tens’ digit and units’ digit isSelect one:• a. 7 • b. 9 • c. 16 • d. 0

If 567567567 is divided by 567, the quotient is

Select one:• a. 111 • b. 10101 • c. 1001001 • d. 3

Note that the choices “look”

similar, but are far apart!

The given number is 567 followed by 6

digits. So the answer choice must be the

one with “1” followed by 6 digits!

19 thousands + 19 hundreds + 19 ones is equal toSelect one:• a. 21090 • b. 20919 • c. 19919 • d. 191919

How many 1/8 are in 1/2 ?Select one:• a. 8 • b. 4 • c. 2 • d. 16

The figure consists of five squares of the same size. The area of the figure is 180 square centimeters. The perimeter (in cm) of the figure will beSelect one:• a. 45 • b. 48 • c. 72 • d. 36

The solid as shown in the figure is made up of cubical blocks each of side 1 cm. The number of blocks isSelect one:• a. 52 • b. 60 • c. 72 • d. 48

Must be a multiple of 5, 4 and 3.

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