Arithmetic Operations Questions and Answers

Answer: D

The meeting was scheduled for 8.05 am.

Work through the times step by step:

\[ \begin{aligned} \text{Asmita arrives} &= 8.30 - 15\ \text{min} = 8.15 \\ \text{Colleague arrives} &= 8.15 + 30\ \text{min} = 8.45 \\ \text{Meeting} &= 8.45 - 40\ \text{min} = 8.05 \end{aligned} \]

The colleague is 40 minutes late, so the meeting began 40 minutes before 8.45 am. Note that Asmita, arriving at 8.15, was herself 10 minutes late. The option 8.15 am is only her arrival time, 8.45 am is the colleague's arrival, and 9.10 am adds the 40 minutes instead of subtracting them.

Answer: C

Sohail has to pay ₹ 100.50.

Add the cost of each item, taking the quantities into account:

\[ \begin{aligned} \text{Crayons} &= 15.50 \\ \text{Pencils} &= 2 \times 14.00 = 28.00 \\ \text{Sketch pens} &= 22.50 \\ \text{Scissors} &= 17.00 \\ \text{Glazed paper} &= 5 \times 2.50 = 12.50 \\ \text{Stickers} &= 5.00 \end{aligned} \]

\[ 15.50 + 28.00 + 22.50 + 17.00 + 12.50 + 5.00 = 100.50 \]

He buys no eraser, so its ₹ 2.00 is not included. Miscounting a quantity gives the distractors: one packet of pencils instead of two gives 86.50, and four sheets of glazed paper instead of five gives 98.00.

Answer: B

The total travel time is 29 hours 35 minutes.

Split the journey at midnights:

\[ \begin{aligned} \text{30 May, 23:40 to 24:00} &= 20\ \text{min} \\ \text{31 May, whole day} &= 24\ \text{h} \\ \text{1 June, 00:00 to 05:15} &= 5\ \text{h}\ 15\ \text{min} \end{aligned} \]

\[ \begin{aligned} \text{Total} &= 20\ \text{min} + 24\ \text{h} + 5\ \text{h}\ 15\ \text{min} \\ &= 29\ \text{h}\ 35\ \text{min} \end{aligned} \]

29 hours 15 minutes is what you get by forgetting the 20 minutes before midnight, and both 28-hour options fall more than an hour short of the true time.

Answer: C

7041 should be subtracted.

First find the sum, then the difference from 17863:

\[ \begin{aligned} 8008 + 8088 + 8808 &= 24904 \\ 24904 - 17863 &= 7041 \end{aligned} \]

Check: 17863 + 7041 = 24904. The option 7141 is off by 100, a typical slip when borrowing in the hundreds column; 6121 and 6131 fail the same check.

Answer: D

The mug holds 320 mL.

Fifty full mugs empty the 16-litre bucket, so one mug holds one-fiftieth of 16 litres. Convert to millilitres first:

\[ \begin{aligned} 16\ \text{L} &= 16000\ \text{mL} \\ 16000 \div 50 &= 320\ \text{mL} \end{aligned} \]

Check: 50 × 320 = 16000 mL. The other capacities are too small: 50 mugs of 250 mL hold only 12.5 litres, 50 of 275 mL hold 13.75 litres, and 50 of 225 mL hold 11.25 litres.

Answer: C

The railway station is 15 km from her home.

The first 2 km cost ₹ 50 together. The rest of the fare pays for the extra kilometres at ₹ 16 each:

\[ \begin{aligned} 258 - 50 &= 208 \\ 208 \div 16 &= 13\ \text{km} \\ 2 + 13 &= 15\ \text{km} \end{aligned} \]

The trap is stopping at 13 km, which counts only the kilometres after the first two. 12 km and 18 km do not fit: 12 km would cost 50 + 10 × 16 = ₹ 210, and 18 km would cost 50 + 16 × 16 = ₹ 306.

Answer: C

The number is 25.

The remainder is 5 and the divisor is twice the remainder, so the divisor is 10. The divisor is also 5 times the quotient, so the quotient is 2. Then use dividend = divisor × quotient + remainder:

\[ 10 \times 2 + 5 = 25 \]

Check: 25 ÷ 10 gives quotient 2 and remainder 5. 15 is divisor plus remainder; 52 and 48 do not leave remainder 5 when divided by 10.

Answer: B

One millimetre is the same as 0.1 cm.

\[ \begin{aligned} 1\ \text{cm} &= 10\ \text{mm} \\ 1\ \text{mm} &= \tfrac{1}{10}\ \text{cm} = 0.1\ \text{cm} \end{aligned} \]

In metres, 1 mm = 0.001 m, since 1 m = 1000 mm. So 0.01 cm is ten times too small, while 0.01 m (1 cm) and 0.1 m (10 cm) are ten and a hundred times too large.

Answer: D

The number to subtract is 2563.

\[ \begin{aligned} 9909 + 9099 + 9009 &= 28017 \\ 28017 - 25454 &= 2563 \end{aligned} \]

Check: 25454 + 2563 = 28017. The other options rearrange the same digits (2356, 2365, 2536) and fail this check.

Answer: B

The cheapest is 750 packets of ₹ 7.50 each.

\[ \begin{aligned} 75 \times 750 &= 56250 \\ 750 \times 7.50 &= 5625 \\ 90 \times 750 &= 67500 \\ 900 \times 7.50 &= 6750 \end{aligned} \]

Here 7.5 dozen is 90 items and 75 dozen is 900 items. The second option costs ₹ 5625, the least; 75 dozen at ₹ 7.50 (₹ 6750) is close but slightly more.