Expressions using Letter-Numbers
Class 7 · Mathematics Part 1 · 17 Questions
Write formulas for the perimeter of: (a) triangle with all sides equal. (b) a regular pentagon (as we have learnt last year, we use the word 'regular' to say that all sidelengths and angle measures are equal) (c) a regular hexagon
Munirathna has a 20 m long pipe. However, he wants a longer watering pipe for his garden. He joins another pipe of some length to this one. Give the expression for the combined length of the pipe. Use the letter-number 'k' to denote the length in meters of the other pipe.
What is the total amount Krithika has, if she has the following numbers of notes of ₹100, ₹20 and ₹5? Complete the following table:
| No. of ₹100 notes | No. of ₹20 notes | No. of ₹5 notes | Expression and total amount |
|---|---|---|---|
| 3 | 5 | 6 | |
| 8 | 4 | z | |
| x | y | z |
Venkatalakshmi owns a flour mill. It takes 10 seconds for the roller mill to start running. Once it is running, each kg of grain takes 8 seconds to grind into powder. Which of the expressions below describes the time taken to complete grind 'y' kg of grain, assuming the machine is off initially?
Write algebraic expressions using letters of your choice. (a) 5 more than a number (b) 4 less than a number (c) 2 less than 13 times a number (d) 13 less than 2 times a number
Describe situations corresponding to the following algebraic expressions: (a) 8 × x + 3 × y (b) 15 × j - 2 × k
Observe each of them and identify if there is a mistake. If you think there is a mistake, try to explain what might have gone wrong. Then, correct it and give the value of the expression. 1. If a = -4, then 10 - a = 6. 2. If d = 6, then 3d = 36. 3. If s = 7, then 3s - 2 = 15. 4. If r = 8, then 2r + 1 = 29. 5. If j = 5, then 2j = 10. 6. If m = -6, then 3(m + 1) = 19. 7. If f = 3, g = 1, then 2f - 2g = 2. 8. If t = 4, b = 3, then 2t + b = 24. 9. If h = 5, n = 6, then h - (3 - n) = 4.
Simplify each of the following expressions:
Some simplifications of algebraic expressions are done below. The expression on the right-hand side should be in its simplest form. Observe each of them and see if there is a mistake. If you think there is a mistake, try to explain what might have gone wrong. Then, simplify it correctly.
One plate of Jowar roti costs ₹30 and one plate of Pulao costs ₹20. If x plates of Jowar roti and y plates of Pulao were ordered in a day, which expression(s) describe the total amount in rupees earned that day?
Pushpita sells two types of flowers on Independence day: champak and marigold. 'p' customers only bought champak, 'q' customers only bought marigold, and 'r' customers bought both. On the same day, she gave away a tiny national flag to every customer. How many flags did she give away that day?
A snail is trying to climb along the wall of a deep well. During the day it climbs up 'u' cm and during the night it slowly slips down 'd' cm. This happens for 10 days and 10 nights. (a) Write an expression describing how far away the snail is from its starting position. (b) What can we say about the snail's movement if d > u?
Radha is preparing for a cycling race and practices daily. The first week she cycles 5 km every day. Every week she increases the daily distance cycled by 'z' km. How many kilometers would Radha have cycled after 3 weeks?
A local train from Yahapur to Vahapur stops at three stations at equal distances along the way. The time taken in minutes to travel from one station to the next station is the same and is denoted by t. The train stops for 2 minutes at each of the three stations. (a) If t = 4, what is the time taken to travel from Yahapur to Vahapur? (b) What is the algebraic expression for the time taken to travel from Yahapur to Vahapur?
Simplify the following expressions:
Add the expressions given below:
Describe situations corresponding to the following algebraic expressions: (a) 8x + 3y (b) 15x - 2x