Question
Find the value of using the short-cut method: $(84)^3$
✓
Answer
$(84)^3$We know that short-cut method for finding the cube of any two digit numbers is as given.
$(a+b)^3=a^3+3 a^2 b+3 a b^2+b^3$
$=a^2 \times a+a^2 \times 3 b+b^2 \times 3 a+b^2 \times b$
Here,
$a = 8$
$b = 4$
$(a+b)^3=a^3+3 a^2 b+3 a b^2+b^3$
$=a^2 \times a+a^2 \times 3 b+b^2 \times 3 a+b^2 \times b$
Here,
$a = 8$
$b = 4$
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A loaded truck covers $16$km in $25$ minutes. At the same speed, how far can it travel in $5$ hours?
→The value of a machine depreciates at the rate of $10\%$ per annum. It was purchased $3$ years ago. If its present value is $Rs.291600,$ for how much was it purchased$?$
→In a public school, $70 \%$ of the student population are boys. If there are $120$ girls, then find the total enrollment of the school.
→2025 plants are to be planted in a garden in such a way that each row contains as many plants as the number of rows. Find the number of rows and the number of plants in each row.
The marks scored by $20$ students in a test are given below: $54, 42, 68, 56, 62, 71, 78, 51, 72, 53, 44, 58, 47, 64, 41, 57, 89, 53, 84, 57.$ Complete the following frequency table:
What is the class interval in which the greatest frequency occurs$?$
→| (Marks in class intervals) | Tally marks | Frequency (no. of children) |
| $40-50$ | ||
| $50-60$ | ||
| $60-70$ | ||
| $70-80$ | ||
| $80-90$ |
A cube $A$ has side thrice as long as that of cube $B?$ What is the ratio of the volume of cube $A$ to that of cube $B?$
→Pipes $A$ and $B$ can fill an empty tank in $10$ hours and $15$ hours respectively. If both are opened together in the empty tank, how much time will they take to fill it completely?
→Pattern $B$ consists of four tiles like pattern A. Write a proportion involving red dots and blue dots in pattern $A$ and $B$. Are they in 
direct proportion? If yes, write the constant of proportion.
→direct proportion? If yes, write the constant of proportion.
A jeweller allows a discount of $16\%$ to his customers and still gains $20\%$. Find the marked price of a ring which costs the jeweller $Rs. 1190.$
→In the given parallelogram $YOUR$, $\angle\text{RUO}=120^\circ\text{and}\ \text{OY}$ is extended to point $S$ such that $\angle\text{SRY}=50^\circ.\text{Find}\angle\text{YSR}.$
→